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Describe why a balloon sticks to the wall after rubbing against your shirt."Rubbing a balloon on your shirt means electrons transfer from your body to the balloon. However the balloon is negative and the wall is originally neutral meaning that the ballon won't stick. The balloon sticks because the electrons in the wall feel a repulsive force from the electrons in the balloon and they move in the opposite direction (further into the wall). This means that the force of attraction is a lot stronger then the force of repulsion and therefore the ballon sticks to the wall.<img src=""paste-055414030f630def2b1ee1b7fd75d9dd9e2fb0ff.jpg"">"electricity
List the 2 ways that cause static electricity.Friction (contact)<div>Induction (non-conduct)</div>electricity
Why do only electrons transfer out of electrons, protobs and neutrons?Electrons move as they are a lot further away from the nucleus of the atom than protons and neutrons are (which are in the nucleus of the atom). This means that the force of attraction in the protons and neutrons is a lot stronger (as they are close together) then the force of attraction in the electrons, so the electrons are more likely to move and are the only particle in an atom that can transfer from one substance to another.&nbsp;electricity
Why does a charged polythene rod attract a metal drinks can after being rubbed against a cotton rag?This is because, when rubbing the cotton rag against a polythene rod, electrons are transferred from the cotton to the polythene rod. When the rod is placed next to the can, the can moves towards the rod. This is because, the electrons in the rod are repelling against the electronsin the drinks can, moving them further away. This means that the protons in the can are closer to the electrons in the rod, and therefore the force of attraction between the EXCESS electrons in the rod and the protons in the can is stronger then that between the EXCESS electrons in the rod and the electrons in the drinks can, meaning that the attraction force is stronger then the repulsion force, and therefore the can attracts to the polythene rod.electricity
Can you charge electrical insulators by rubbing them together?Yes.
Can you charge electrical conductorsNo.electricity
How can you test to see if a material is an electrical conductor or an electrical insulator?Using crocodile clips, place material X in a circuit containing a battery and a light bulb. If the bulb lights up, the material is an electrical conductor. If the bulb doesn't light up, the material is an electrical insulator.electricity
What happens when you rub a plastic ruler against your jumper and then hold close to small pieces of paper and why?When the ruler is rubbed against your jumper, the ruler becomes charged (we assume positively charged). If the ruler is held close to some small, uncharged pieces of paper, some electrons within the paper will be attracted to the edges closest towards the ruler. There willl therefore be an attraction between the negative parts of the paper and the positive ruler.electricity
How does electrostatic paint spraying work?As drops of paint emerge fromt he spray gun, they are charged. As the drops all carry the same charge they repel eachother and spread out forming a thin spray. The object (metal bike frame in this case) has a wire attached to an electrical supply giving the frame the opposite charge. The paint drops are therefore attracted to the surface of the frame. There is the added benefit that paint is attracted into places, such as corners, that would normally be hard to reach. Furhtermore, less paint is wasted and/or is left on the floor. This is because, even if th paint is sprayed far into the atmosphere, it can still coat the front or back of the object as the force of attraction between the paint drops and the object is so strong.electricity
Why do aircarft have to be earthed before being refuelled?This is because, when refuelling an aircraft, the fuel moving through pipe connecting the plane and the fuel tanker rubs against the inside of the pipe, causing an electrostatic build up via friction (both materials are electrical insulators). This build up occurs in the fuel, which takes the charge to the aircraft which charges the aircraft. To counter this charge, both the aircraft and the tanker need to be electrically connected together (by a wire) and earthed. No matter which charge the plane is, the earth has so much charge that it can counter any charge within the aircraft. If the plane wasn't earthed, the charge in the fuel could create a fire within the plane.electricity
How to inkjet printers work?Many modern inkjet printers use inkjets to direct a fine jet (stream) of ink drops onto paper. They do this by using electrostatic forces. Each spot of ink is given a charge so that it falls between a pair of deflecting plates and electrostatic forces direct it into the correct position.&nbsp; The charges on the plates change hundreds of times each second&nbsp; so that each drop falls in a different position, forming pictures and words on the paper as required. By controlling the voltage on each plate, a particular ink drop can be precisely positioned on the piece of paper. For example, if the plate on the left was very positively charged and the plate on the right was very negatively charged and the ink drop was negatively charged, the drop would end up on the far left of the paper.&nbsp;electricity
How might a plane explode when landing and how is this solved?As aircraft fly through the air, friction causes them to become chared with static electricity. After an aircraft has landed, there is a possibility of charges escaping to the earth as a spark or flash of electricity. If this takes place when the plane has lots of fuel in it, it could cause an explosion. The solution to this problem is to earth the plane with a conductor of electricity as soon as the plane lands.electricity
How does lightning work?Water molecules and ice particles undergo convection in clouds and cause a charge distribution (meaning one side becomes positive and one side becomes negative). The excess charge can be depositied via either lightning or through a lightning conductor. Lightning normally happens within clouds when the positive particles at the top of the clouds attract the negative electrons at the bottom. However, sometimes positive charge from the earth risies up into tall structures like skyscrapers or trees and attracts the electrons in the bootm of the clouds. When these positive and negative charges meet, a bolt of light is formed which is lightning.electricity
How do electrostatic precipitators work?As the smoke initially rises up the chimney, it passes through a mesh of wires that are highly negatively charged. As they pass through the mesh, the ash and dust particled become negatively charged. Higher up the chimney, these charged particles are attracted by and stick to large metal earthed plates. The cleaner smoke is then released into the atmosphere. When the earthed plates are completely covered with dust and ash, they are tapped hard, like a hammer. The dust and ash fall into collection boxes, which are later emptied.electricity
How do photocopiers work?Positive charges are sprayed onto a turning drum whose surface is covered with a metal called selenium. A bright light is shone onto the sheet of paper to be copied. The white parts fo the paper reflect light onto the drum whereas the dark or printed parts do not. In those places where light is reflected onto the drum the selenium loses its charge, but where no light is reflected onto the drum the charge remains. A negatively charged carbon powder called toner is blown across the drum and sticks to those parts of the drum that are charged. A sheet of paper is now pressed up against the drum and picks up the pattern of the carbon powder. The powder is then fixed into place by a heater.electricity
Define electrical current.Electrical current is the rate of flow of charge.electricity
List the meaning and symbol for Q, I, and T.Q = Charge (Coulombs) (C)<div>I = Current (Amps) (A)</div><div>T = Time (Seconds) (s)</div>electricity
List the equation for current and ways to rearrangement.Current = the amount of charge transferred/time<div><br></div><div>(I = Q/t)<br><div><br></div><div>The amount of charge transferred = current x time</div><div><br></div><div>(Q = I x t)</div><div><br></div><div>Time = the amount of charge transferred/current</div></div><div><br></div><div>t = Q/I</div>electricity
What is significant about current in a series circuit?In a series circuit, current (which should be equal to the supply current) is the same at all points.electricity
What is significant about current in a parallel circuit?In a parallel circuit, the sum of current in each branch equals the supply current.electricity
What is voltage?Voltage is the measure of energy per unit charge.electricity
What is the equation for voltage and rearrange it and what to the symbols stand for and what are they measured in?V = E/Q<div>Q= E/V</div><div>E= Q x V</div><div><br></div><div>V = Voltage (Volts) (V)</div><div>E = Energy (Joules) (J)</div><div>Q = Charge (Coulombs) (C)</div>electricity
What does emf stanf for and what is it?emf stands for the Electro Motive Force. It is the enrgy per unti charge (voltage) supplied by the source (usually the battery).electricity
What does pd stand for and what is it?pd stands for potential difference. It is the enrgy per unit charge dussipated by an external component.electricity
What is significant about the pd's in a series circuit?In a series circuit, the sum of pd's equals the emf.electricity
What is significant about the pd's in a parallel circuit?In a parallel circuit the pd's are all the same across the components and these pd's should be equal to the emf.electricity
What do we call plastics and metals in relation to electricity and why?Electrons flow easily through all metals. We therefore describe metals as being good conductors of electricity, and they are generally known as electrical conductors.<div><br></div><div>Electrons do not flow easily through plastics. We therefore describe plastics as being good insulators of electricity, and they are generally known as electrical insulators.</div>electricity
Give an example of a good electrical insulator and why we would want it to be like this.The casing of a plug as we want to prevent the flow of charge in a plug.electricity
Why is there current if electrons in metals usually move in random directions?Because, if a cell or battery is connected across the conductor (metal), more of the electrons now flow in the direction away from the negative terminal and towards the positive terminal than in the opposite direction. We say 'there is now a net flow of charge.'electricity
Why are charges unable to move through insulators?As all the electrons are held tightly in position and are unable to move from atom to atom in electrical insulators.electricity
What do we use to measure the size of the current and how is it connected to the circuit and why dies the ammeter have almost no effect on the current?We measure the size of the current in a circuit using an ammeter. The ammeter is connected in series with the part of the circuit that we are interested in. It has a very low resistance and so has almost no effect on the current.electricity
How many electrons are in 1C of charge?6 x 10 to the power of 18 electrons.electricity
What does it mean if there is a current of 1A in a wire?It means that 1C of charge is passing along the wire each second.electricity
What does voltage actually measure?The amount of energy given to the charges/electrons by a cell or battery.electricity
What does it mean if a 1.5V cells is connected to a circuit, and current flows?It means that 1.5J of energy is given to each coulomb of charge that passes through the cell.electricity
What is a volt equal to?A Joule per Coulombelectricity
What happens as charges flow around a circuit?As the charges flow around a circuit, the energy they carry is transferred by the components they pass through. For example, when current passes through a bulb, energy is transferred to the surroundings as heat and light. When the current passes through the speaker of a radio, most of the energy is transferred as sound.&nbsp;electricity
What does the voltage tell us in the external part of a circuit (outside the cell or battery)?In the external part of a circuit (outside the cell or battery), the voltage across each component tells us how much energy it is transferring. If the voltage across a component is 1V, this means that the component is teansferring 1J of energy each time 1C of charge passes through it.electricity
If E = QxV and Q = Ixt, what does this mean.That E - I x t x Velectricity
What does a voltmeter measure and how is it connected in a circuit?We measure voltages using a voltmeter. This is connected across in parallel with the component we are investigating. A voltmeter connected across a cell or battery&nbsp; will measure the energy given to each coulomb of charge that passes through it. A voltmeter connected accross a component will measure the electrical energy transferred when each coulomb of charge passes through it.electricity
How do you test if a circuit 'is on' or 'is working'?We sometimes put a small bulb or lamp in a circuit to show us if a circuit is 'turned on'. When there is a current in the circuit, the bulb glows or shines.&nbsp;electricity
What is a parallel circuit?A circuit that has branches and junctions and more than one path that the current can follow.electricity
What is a series circuit?A circuit where there are no branches or juctions, and therefore means there is only one path the current can follow.electricity
What is significant about the size of current in a series circuit?The size of current in a series circuit depends on the voltage supplied to it, and the numebr and type of the other components&nbsp; in the circuit. If a second identical cell is added in series the voltage will double double so the current will also double.electricity
What happens to current in a parallel circuit?In a parallel circuit, the currents will not be the same in different parts of the circuit. The types of components in each of the different parts will affect the currents. In a parallel circuit, the number of electrons that flow into a junction each second must be equal to the number that leave each second. This means that the currents entering a junction must always be equal to those that leave. For example, if the current that enters a junction is 0.6A, the current that leaves must also be 0.6A.electricity
List some things that can happen in a series circuit containing bulbs.One switch placed anywhere in the circuit can turn all the bulbs on and off.&nbsp;<div><br></div><div>If any one of the bulbs break, it causes a gap in the circuit and all of the other bulbs will 'stop working.'</div><div><br></div><div>The energy supplied by the cell is 'shared' between all the bulbs, so the more bulbs you add to a series circuit, the less bright they all become.</div>electricity
List some features about parallel circuits that contain bulbs.Switches can be placed in different parts of the circuit to switch each bulb on and off individually, or all together.<div><br></div><div>If one bulb breaks, only the bulbs on the same branch of the circuit will be affected.</div><div><br></div><div>Each branch of the circuit receives the same voltage, so if more bulbs are added to a circuit in parallel, they all still keep the same brightness.</div>electricity
Why are decorative lights often wired in series?Because each bulb only ususally needs a low voltage, so even when the voltage from the mains supply is 'shared' out between them, each bulb still gets enough energy to produce light. Unfortunately, if the filament in one of the bulbs breaks, then all the other bulbs will go out.electricity
Why do we know that the lights in our home are wired in parallel?Because the lights in our home can be switched on and off seperately, and the brightness of each light does not change when other lights are on and off. Also, if a bulb breaks or is removed, you can still use the other lights.electricity
Does current the path with the least or most resistance?Leastelectricity
Define resistance.Resistance is the ability of a material to slow down current by removing energy from the current. It is measured in ohms.electricity
Why does resistance increase if a wire is heated?Because as the wire heats up, the atoms in the wire move around more/quicker, making it harder for the electrons/current to pass through.electricity
Why do wires heat up slightly in a working circuit?Tgis is because, as electrons move down the wire, they collide into the atoms in the wire, meaning those atoms in the wire move quicker and the wire heats up slighty.electricity
State the equation linking, resistance, current and voltage and rearrange it.V = I x R (voltage = current x resistance)<div>I = V/R (current = voltage/resistance)</div><div>R = V/I (resisatnce = voltage/current)</div><div><br></div><div>Voltage is measured in volts (V)</div><div>Current is measured in amps (A)</div><div>Resistance is measured in ohms (Ω)</div>electricity
What is significant about current and potential difference in an ohmic conductor?In an ohmic conductor, (obeys Ohms law) the current is directly proportional to the applied potential difference for constant physical conditions (note: temperature must be constant).electricity
Why can we describe connecting wires as havng very low resistance?Because connecting wires allow charge to pass through them very easily, and this charge loses very little of its energy as it passes through.electricity
What can we say about components that have a high resistance?That the flow of charge through high resistance components is not easy, and a large amount of energy may be used to move the charges through them. The enrgy that is transferred to move the charges through the high resistance components is usually transferred as heat energy.electricity
What is significant about the relationship between current and voltage?It is directly proportional.electricity
What does it mean if the gradient is steeper on a current/voltage graph for a wire.The steeper the gradient, the lower the resistance of a wire.electricity
What is significant about the current/voltage graph for a wire or resistor?The graph is a straight line, with a constant gradient. Therefore, the resistance of thos component does not change.&nbsp;electricity
What is significant about the current/volatage graph for a filament bulb?"<img src=""ele10.png"">This graph is not a straight line. The resistance of the bulb changes. At higher currents and voltages the slope of the graph shows us that the resistance of the filament bulb increases - that is, as the temperature of the filament bulb increases, the current decreases."electricity
What is significant about the current/voltage graph for a diode?"<img src=""lBlrZ.png"">This strangely shaped graph shows that diodes have a high resistance when the current is in one direction and a low resistance when in the opposite direction."electricity
What do fixed resistors do?Fixed resistors are included in circuits in order to control the sizes of currents and voltages.&nbsp;electricity
What could happen in a circuit without a fixed resistor?The voltage across a component (e.g bulb) may cause too large a current and the bulb may break.electricity
Why are variable resistors called variable resistors and what are they used in?Variable resistors are called variable resistors as it is possible to alter their resistance. If you alter the volume of your radio using a knob you are using a variable resistor to do this.electricity
What can variable resitors be used to control in circuits with a bulb and how does resistace affect the brightness of the bulb?If the resistance is decreased there will be a larger current and therefore the bulb will shine more brightly. If the resistamce is increased there will be&nbsp; asmaller current and therefore the bulb will glow less brightly or not at all. The variable resistor is behaving in this circuit as a dimmer switch.electricity
What can a variable resistor be used to control in a circuit containing electric motors?It can be used to control the speed of the motor.electricity
What is a thermistor and what does the resistance/temperature graph look like for it?"A thermistor is a resistor whose resistance changes quite a lot even with small changes in temperature.<img src=""thermistor_graph.png"">"electricity
What are thermistors used in?Thermistors are used in temperature sentitive circuits in devices such as fire alarms. They are also used in devices where it is important to make sure there is no change in temperature, for example, in freezers and computers.electricity
What is a light-depedant resistor (LDR)?A light dependant resistor is a resistor whose resistance changes when light is shone on it. In the dark its resistance is high but when light is shone on it its reistance decreased.electricity
What are LDR's often used in?LDR's (light-dependant resistors) are often used in light-sensitive circuits in devices such as photographic-exposure equipment, automatic light controls and burglar alarms.electricity
What are diodes?Diodes are semiconductive devices that allow charges to flow through them easily but only in one direction.electricity
What is significant about the way the diode is put in a circuit?When a diode is connected the 'right' way round, the diode offers little rsistance to the charges flowing through it. Therfore, in a circuit with a bulb, the current reamins quite high and the bulb lights up. However, if the diode is connected the opposite way round, the diode has a very high resistance and the rate at which the charges can flow through the diode is much less, and therefore the current is very small and in a circuit with a bulb in it, the bulb would not light.electricity
What are diodes often used in?Diodes are often used in circuits where there it is important that electrons flow in only one direction. For example, they are used in rectifier circuits, that convert alternating current into direct current. Some diodes glow when charges flow through them. They are called light emitting diodes.electricity
List a useful way to remember how diodes work.Diodes are like airplane steps - from the ground, you can only climb them in one direction. In a diode the charge can only flow in one direction.electricity
"What is this and what does it do?<img src=""open_switch-159070B51552F5863F2-thumb400.png"">"An open switch (circuit won't work when switch is open). A switch turns the circuit on or off, or lets the current flow through the circuit.electricity
"What is this?<img src=""screen_shot_2013-05-16_at_115721-13EACFF88C8632BEA34.png"">"Closed switch (circuit will work when switch is closed)electricity
"What is this?<img src=""screen_shot_2013-05-16_at_115727-13EACFFCC4A4283D7D2.png"">"A cellelectricity
"What is this and what does it do?<img src=""4-battery-schematic-symbol-article-examples.png"">"A battery. A battery is a source of energy which provides a voltage to get the current flowing in a circuit.electricity
"What is this and what does it do?<img src=""fig1.jpg"">""A diode. A diode is a resistor that only&nbsp;<span style=""color: rgb(35, 31, 32);"">allows current to flow in one direction only.&nbsp;</span>"electricity
"What is this and what does it do?<img src=""resistor.jpg"">""A resistor.&nbsp;<span style=""color: rgb(35, 31, 32);"">A&nbsp;</span>resistor<span style=""color: rgb(35, 31, 32);"">&nbsp;is an electrical component that restricts the flow of electric current.</span>"electricity
"What is this and what does it do?<img src=""fig3.jpg"">""A variable resistor.&nbsp;<span style=""color: rgb(70, 70, 70);"">A variable resistor is a resistor of which the electric resistance value can be adjusted.</span>"electricity
"What is this?<img src=""screen_shot_2013-05-16_at_115934-13EAD024A9725782A76.png"">"A bulbelectricity
"What is this and what does it do?<img src=""Fuse-symbol.png"">""A fuse.&nbsp;<span style=""color: rgb(35, 31, 32);"">The fuse breaks the circuit if a fault in an appliance causes too much current to flow.</span>"electricity
"What is this and what does it do?<img src=""screen_shot_2013-05-16_at_115927-13EAD01EB4A681B2B0D.png"">"A voltmeter. Voltmeters measure the potential difference of an external component or the emf if it is placed in parallel to a cell/battery.electricity
"What is this and what does it do?<img src=""sTYoJ.png"">"An ammeter. The ammeter can measure the current at any point in the circuit.electricity
"What is this and what does it do?<img src=""small.png"">"A thermistor. In a circuit, thermistors are used as temperature sensors, and in most thermistors, their resistance decreases as temperature increases.electricity
"What is this and what does it do?<img src=""800px-Light-dependent_resistor_schematic_symbol.svg.png"">"A light-dependant resistor (LDR). LDR's are used to detect light levels, for example, in automatic security lights. Their resistance decreases as light intensity increases.electricity
What is a filament lamp and how does it work?A filament lamp is a common type of lightbulb. It contains a thin coil of wire called the filament. This heats up when an electric current passes through it, and produces light as a result.electricity
Which substaances are conductors of electricity?All metals ans alloys.<div><br></div><div>All aqueous solutions.</div>
List some adavnatages and disadvantages of wind power?Advantage:<div><br></div><div>It is a renewable source so it doesn't produce greenhouse gases and therefore doesn't contribute to global warming.</div><div><br></div><div>The energy produced is clean.</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Wind power can only be harvested in regions where the wind blows with enough energy for a significant proportion of the year.</div><div><br></div><div>Wind farms can cause environmental damage, as they can change the appearance of the landscape.</div><div><br></div><div>They cause some noise pollution.</div><div><br></div><div>They may kill birds and bats.</div>energy-resources-and-electricity-generation
How does wind power work?Winds are powered by the suns heat energy. Windmills have been used to grind corn and power machinery like pumps to drain (remove liquid from) lowland areas. Today, wind turbines drive generators to provide electrical energy.energy-resources-and-electricity-generation
What are photovolataic cells, what do they do, and how to they work and why are more PV energy farms being set up?Photovoltaic cells are solar cells that transfer light energy directly to electrical energy. PV (photovoltaic) cells are around 15% efficient, meaning that around 15% of the suns energy is transferred to useful electrical energy. Improvements in PV efficiency and the fact that they are becoming cheaper to produce mean that more PV energy farms are being set up to provide large amounts of electrical energy. PV cells are also used to provide small amounts of electricity for use in places that cannot easily be connected to the electricity mains supply.energy-resources-and-electricity-generation
List the advantages and disadvantages of photovoltaic cells.Advantages:<div><br></div><div>They provide a renewable energy source that does not produce greenhouse gases and therefore does not contribute to global warming.</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Some people think that large PV energy farms spoil the countryside.</div><div><br></div><div>Some think that good farming land is lost when PV energy farms are built.</div>energy-resources-and-electricity-generation
What is geothermal energy and how does it work?Geothermal energy is thermal energy stored deep inside the earth. In some areas of the world, like Iceland, geothermally heated water is readily available in springs and geysers. This is used to drive turbines in electricity generation stations and generate electricity. The hot water is also used to provide domestic heating by sending it directly to houses. There are many areas of the world where geothermally heated springs can, and are, being used to provide energy.energy-resources-and-electricity-generation
List the advantages and disadvantages of geothermal energy.Advantages:<div><br></div><div>Geothermal energy is a renewable energy source, so it does not produce greenhouse gases and therefore does not contribute to global warming.</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Geothermal pumps (that pump the hot water and heat) can be expensive to install.</div>energy-resources-and-electricity-generation
What is significant about the cost of energy per unit of fuel for nuclear power and why is this the case?Planners must also look at the financial cost of electricity generation. Nuclear power uses a relatively cheap fuel and uranium produces huge amounts of energy, so the cost of energy per unit of fuel used is low.energy-resources-and-electricity-generation
Why is building a nuclear power station expensive?This is because, nuclear power requires complex technology and very high standards of safety. On top of these 'start up' costs, the planners must also consider the expense of decommissioning a nuclear power station at the end of its working life. For conventional power stations, this is a routine demolition job, but for nuclear power stations the task is not aas straight forward. Radioactive materials must be handles with great care and stored in a way to ensure that none escape.energy-resources-and-electricity-generation
<div>What is payback time and why is the payback time for nuclear power stations very long?</div><div>Thw payback time is how long it takes for the income from selling electricity to cover the cost of building the power station.</div><div><br></div>We see that, although the running costs of nuclear power are very low, the payback time is very long.energy-resources-and-electricity-generation
Why is the payback time for wind generators quite long?The cost of setting up a wind farm is much lower then the cost of vuilding a nuclear power station and there are no fuel costs. However, the amount of energy produced by wind farms is comparitively low. The payback time for wind generators is therefore quite long.energy-resources-and-electricity-generation
What is wave energy and how does it work?Energy can also be extracted by waves. The continuous movement the surface of the seas and oceans is a result of a combination of tides and winds. Again, wave energy is renewable, as the movement energy of the waves is continuously available. A variety of methods have been developed to make use of the rise and fall of water due to waves. For example:<div><br></div><div>A rising water colum pushes air pass a turbine, spinning it which drives a generator. The water level then falls because of waves, which sucks the air back past the turbine, which spins again and subsequently drives a generator again. This generator produces electricity.</div>energy-resources-and-electricity-generation
What are the advantages and disadvantages of wave energy?Wave power is clean, producing no greenhouse gases and therefore not contributing to global warming.<div><br></div><div>Some fish can get trapped in the wave column and killed by the spinning turbine.</div>energy-resources-and-electricity-generation
What is tidal energy and how does it work?The tides also involve the movement of huge amounts of water. Tidal power generation schemes generate power by turning turbine as the tide moves into a dammed (blocked) river estuary (an estuary is where a river joins the sea). As the tide falls and the water flows out the estuary, the turbines turn again.energy-resources-and-electricity-generation
How is the energy sourced for tidal power?The energy for the movement of the tides is provided by the gravitational pull of the moon and sun. This is renewable energy using a small fraction of the continuous supply of gravitational energy.energy-resources-and-electricity-generation
What are the advantages and disadvantages of tidal energy?Advantages:<div><br></div><div>Tidal energy is a renewable energy source and therefore does not produce greenhouse gases and therefore does not contribute to global warming.<div><br></div><div>Disadvantages:</div><div><br></div><div>There are many places around the world suitable for building dams for tidal energy. If a dam is built, it affects the rise and fall of water in the estuary, and this is likely to damage habitats for wildlife.</div></div>energy-resources-and-electricity-generation
What is hydroelectric power and how does it work?The kinetic energy available in large quantities of moving water has been used for many years. Turbines, a kind of water wheel, are used to turn the generators in hydroelectric power stations. These power stations use the stored GPE (gravitational potential energy) of water in high resevoirs built in mountains. The GPE is transferred to KE (kinetic energy) as the water flows down the mountain to the power station below.energy-resources-and-electricity-generation
Why is hydroelectric energy renewable?Hydroelectric energy is renewable. This is because, the sun causes water to evaporate continuously and to be drawn up into the atmosphere. This water then falls as rain to be collected in resevoirs and used again. Therefore, moving water is a renewable source.energy-resources-and-electricity-generation
List some advantages and disadvantages of hydroelectric power.Advantages:<div><br></div><div>It is a renewable source so does not produce greenhouse gases and therefore does not contribute to global warming.</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Building resevoirs and power stations for hydroelectric power can spoil the landscape.</div><div><br></div><div>The resevoir may also destroy or alter the natural habitat for wildlife.</div>energy-resources-and-electricity-generation
What is a renewable energy source?An energy source that will not run out.energy-resources-and-electricity-generation
Why is nuclear power a non renewable source?Nuclear power is a non renewable source because nuclear reactors use uranium to porduce energy. For the nuclear process, a parricular isotope of uranium is needed. Although a reactor only needs a small amount of uranium fuel, uranium is in limited supply as the uranium in the earth was formed befire the solar system was formed, so once it has been used up there will be no further supplies. It is therefore, a nother example of a non-renewable source.energy-resources-and-electricity-generation
List the advantages and disadvantages of nuclear power.Advantages:<div><br></div><div>Power generated from the nuclear processes is clean as the process does not involve the production of greenhouse gases or other polluting gases.</div><div><br></div><div>The cost per unit of electricity is very low.</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Nuclear power stations are expensive to build.</div><div><br></div><div>There is a risk of accidents.</div><div><br></div><div>It is hard to dispose of radioactive material once a power station is finished with/decommissioned.</div><div><br></div><div>Accidents that lead to a release of radioactive materials like uranium and plutonium into the atmosphere pose long-lasting risks to living things including humans.</div>energy-resources-and-electricity-generation
Is electricity an energy resource and why?No, electricity is not an energy resource. This is because, it has to be generated using other resources of energy. Electricity can be generated from renenwable and non-renewable energy resources.energy-resources-and-electricity-generation
How do most power stations work?Heat from nuclear fuel and burning fossil fuels is used to heat water, producing high pressure steam that has a thermal store, which drives the turbine, making its blades spin. The rotating turbine now has a kinetic energy store, and this turbine turns the generator, which gives the generator a kinetic energy store. This generator then transfers the kinetic energy into electrical energy, and this is what produces electricity.energy-resources-and-electricity-generation
What is a non-renewable energy resource?A non renewable energy resource is one that effectively cannot be replaced once it has been used.energy-resources-and-electricity-generation
How does burning fossil fuels affect the environment?Burning fossil fuels affects the environment, mainly by releasing carbon dioxide into the eatmosphere. Carbon dioxide is a greenhouse gas. Greenhouse gases trap the sun's heat in the earth's atmosphere and cause the avergae temperature of th eatmosphere to rise. This effect is called global warming and causes changes in the world's climate and melting of the polar ice caps.energy-resources-and-electricity-generation
How is acid rain formed?Most types of coal and oil contain sulfur. When they are burned, this is converted to sulfur dioxide. Sulfur dioxide is then released into the atmosphere where it combines with water to form acid rain and acid rain causes damage to people, plants and buildings. However, there are ways to remove sulfur dioxide from these fossil fuels and from the atmosphere.energy-resources-and-electricity-generation
List examples of why energy companies need to be able to cope with changes in demand and list the consequences if they can't.The demand for electricity can vary every hour, day or season. For example, there is a rise in electricity demand in the morning, as people wake up, turn on lights and heaters and start to make breakfast. There is also obviously an increase in the demand for heat in the winter compared to the summer. However, some sudden rises in demand are less predictable like when an exciting episode of a new TV show comes out and keep millions of viewers in front of their televisions.<div><br></div><div>The companies that supply electricity must be able to cope with these changes in demand, otherwise they are forced to cut off electricity to some consumers, worsening customer relations, and obviously leading to a reduction in the amount of electricity sold.</div>energy-resources-and-electricity-generation
Why can't nuclear power stations meet sudden variations in demand?As nuclear power stations cannot be turned on instantly and the process of starting the fission reaction and heating up the core if the nuclear reactor is a long one.energy-resources-and-electricity-generation
How does wind and tidal power cope with high demand and why?Wind power is dependant on the strength, direction and frequency of the wind. Although wind farms are located in windy areas, they cannot be relied upon to produce electricity at the times when it is needed most.&nbsp;<div><br></div><div>Tidal power is not available continuously, but the times at which it will be available are predictable.</div>energy-resources-and-electricity-generation
How do power stations that burn fossil fuels cope with increased supply and demand?Power stations that burn fossil fuels can be started more quickly but can still take many hours to start producing electricity. Coal fired station take longer than oil fired stations to develop the heat required to drive steam through the turbines. Gas fired stations can respond most quickly to rises in demand.&nbsp;energy-resources-and-electricity-generation
How to hydroelectric power stations cope with increased supply and demand?Hydroelectric power stations provide a very reliable energy resource with the advantage of being able to respond very quickly to changes in the national demand for electricity. Unlike other types of power station, they are able to operate in reverse. This means that they can use extra electricity produced by other power stations that cannot be shut down quickly to pump water back up into the high level resevoirs. This transfers the electrical energy back to the gravitational potential energy, which can then be re-transferred when needed at a later time. This is th eonly realistic way of 'storing' large amounts of extra electrical energy.energy-resources-and-electricity-generation
How can electricity be generated by solar heating?Electricity can also be generated using solar heating. Curved mirrors are used to focus thermal radiation onto a boiler or pipes containing water to produce steam. The mirrors are controlled to reflect the sun's heat onto the central tower throughout the day, The steam can then be used to drive turbines which can be uses to drive electricity generators.energy-resources-and-electricity-generation
How do solar heating panels work?In a solar heating panel, water is pumped through copper pipes fixed onto a copper sheet. Copper is used because it is an excellent thermal conductor (conductor of heat). The surfaces of the sheet and the pipes have a matt (not shiny) black finish as this is the best absorber of infra-red (heat) radiation. The glass traps a layer of air above the copper to help insulate the unit and keep the heat. The backing is also designed to stop heat escaping to the surroundings. This kind of panel is reasonably efficient and the enrgy produced is more cost efficient than that from photovoltaic cells. Solar heating panels are used widely to provide water heating.energy-resources-and-electricity-generation
Where does the independant variable always go on a graph?On the x axis.electricity
What are the IV characteristics of a filament bulb?As the voltage of the filament lamp increase, the current running through it also increases. This increases the temperature of the filament (the wire in the lamp), increasing the resistance and therefore, the gradient decreases.electricity
What is the point called on the IV graph for a diode where current starts to pass through the diode?The threshold voltage. No current flows below the threshold voltage.electricity
How does most electricity get to your house?The electricity usually enters our homes through an underground cable. This cable is connected to an electricity meter, which measures the amount of electrical energy used. From here, the cable is connected to a consumer unit or a fuse box, which contains fuses or circuit breakers for the various circuits in your home.&nbsp;<div><br></div><div>Most of the wires that leave the box are connected to ring main circuits that are hidden in the walls or floors around each room. Individual pieces of electrical equipment are connected to these circuits using plugs.</div>electricity
What are ring main circuits and what do they usually consist of?Ring main circuits are hidden in the walls or floors around each room. Individual pieces of electrical equipment are connected to these circuits using plugs.<div><br></div><div>Ring main circuits usually consist of three wires - the live wire, the neutral wire and the earth wire.</div>electricity
How is mains electricity supplied to us?By power stations.electricity
What is the purpose of the live, neutral and earth wire?Live wire - The live wire provides the path along which the electrical energy from the power stations travels.<div><br></div><div>Neutral wire - The neutal wire completes this circuit.</div><div><br></div><div>Earth wire - The earth wire usually has no current in it. It is there to protect you if an appliance develops a fault. It provides a path for current to escape without passing through the user.</div>electricity
What is the mains electricity supplied to homes in the UK, China, India and many other countries and why is it dangerous if you come in contact with mains electricity and how is this prevented?Between 220V and 240V. This is a much higher voltage than the cells and batteries used in mobile electrical appliances. If you come into contact with mains electricity, you coud receive a severe electric shock, which might even be fatal. To prevent this, the outer part of the plug, called the casing, is made from plastic, which is a good electrical insulator.electricity
How are conections to the circuits made and why?Connections to the circuits are made via three brass pins, as the metl brass is an excellent conductor of electricity.electricity
"Complete the labels.<img src=""paste-df8308b158097bc25135dd80efa044c5f7f54e20.jpg"">"1. Earth wire - protects the user if there is a fault.<div>2. Live wire - electrical energy travels through this wire to the appliance.</div><div>3. Fuse - breaks up the circuit and stops electricity/current flowing if fault in the appliance causes this current to be too high.</div><div>4. Neutral wire - Completes the circuit.</div><div>5. Cable grip - So the circuit doesn't break if someone pulls the plug out by the wire.</div><div>6. Outer insulation - To protect one from an electric shock.</div>electricity
What colour are the live, neutral and earth wires respectively?Brown, Blue, Yellow and Green.electricity
Which is a.c and which is d.c on a graph?a.c is the wavy line and d.c is the straight line.electricity
Describe how earth wires work in detail.Many appliances have a metal casing. This should be connected to the earth wire so that if the live wire becomes damaged or breaks and comes into contact with the casing the earth wire provides a low-resistance path for the current. This current is likely to be large enough to blow the fuse and turn the circuit off. Without the earth wire, anyone touching the casing of the faulty appliance would receive a severe electric shock as the current passed through them to earth.electricity
How does double insulation work?Some modern appliances now use casinga made from an insulator such as plastic rather than from metal. If all the electrical parts of an appliance are insulated in this way, so that they cannot be touched by the user, the appliance is said to have double insulation. Appliances that have double insulation use a two-wire flex. There is no need for an earth wire.electricity
How do fuses work in detail?Many plugs contain a fuse. The fuse is usually in the form of a cylinder or cartridge, which contains a thin piece of wire made from a metal that has a low melting point. If there is too large a current in the circuit, the fuse wire becomes very hot and melts. The fuse 'blows'. The circuit is now incomplete so there is no current. This prevents you getting a shock and reduces the possibility of an electrical fire. Once the fault causing the increase in current has been corrected, the blown fuse must be replaced with a new one of the same size before the appliance can be used again.electricity
List common fuse sizes and how to choose the correct fuse.There are several sizes of fuses. The most common for domestic appliances in the UK are 3A, 5A, and 13A. The correct fuse for a circuit is the one that allows the correct current but blows if the current is a little larger. If the correct current in a circuit is 2Am then it should be protected with a 3A fuse. If the correct current is 4A then a 5A fuse should be used. It is possible to calculate the correct size of fuse for an appliancebut nowadays manufacturers provide appliances already fitted with the correct size of fuse.electricity
How do modern safety devices work in detail?Modern safety devices, such as those you might find in your consumer unit, are often in the form of trip switches or circuit breakers. If too large a current flows in a circuit a switch automatically opens, making the circuit incomplete. Once the fault in the circuit has been corrected, the switch is reset, usually by pressing a reset button. There is no need for the switch or circuit breaker to be replaced, as there is when fuses are used.&nbsp;electricity
Why is the earth pin on a socket longer then the live and neutral pins?Because when the plug is pushed into a socket, the earth pin pushes against a safety gate to open it and allow access to the other terminals. The safety feature prevents people from sticking their fingers into sockets and receiving an electric shock.electricity
What is d.c?d.c is direct current (current that only travels in one direction).electricity
What is a.c?a.c means alternating current (current that changes direction).electricity
"What is this the symbol for?<img src=""Double-insulated-symbol.png"">"Double insulation.electricity
Define power and what does this mean?The power of an appliance (P) tells you how much energy it transfers each second. This means that the total energy (E) transferred by an aPpliance is eaqual to its power multiplied by the length of time (s) that this appliance is being used.electricity
What can E also be used to and why?E = I x V x t.<div><br></div><div>because</div><div><br></div><div>E = P x t</div><div>P = I x V</div>electricity
Why is a 70W bulb brighter then a 50W bulb?Because although both bulbs transfer electrical energy to heat and light, the 70W bulb will be brighter because it transfers 70J of electrical energy per second, comapred to the dimmer 50W bulb, which only transfers 50J of energy every second.<div><br></div><div>In short, the 70W bulb has a higher power rating.</div>electricity
How many watts in a kilowatt, what is power mesured in and list an equation for it and its rearrangements?1kW = 1000W<div><br></div><div>Power is measured in joules per second or watts (W).</div><div><br></div><div>The power of an appliance is related to the voltage (V) across it and the current (I) flowing through it.</div><div><br></div><div>The equation is: P = IV</div><div><br></div><div>or&nbsp;</div><div><br></div><div>I = P/V</div><div><br></div><div>or</div><div><br></div><div>V= = P/I</div>electricity
Why must switches be placed in the live wire in mains circuits?Switches in main circuits should always be placed in the live wire so that when the switch is open, no energy in the form of electricity can reach an appliance. If the switch is placed in the neutral wire, energy can still enter a faulty appliance, and could possible cause an electric shock.electricity
Compare the wiring in a house and the wiring in an appliance such as a kettle or a toaster?The wiring in a house is designed to let current pass through it easily. As a result, the wires do not become warm when appliances are being used. We therefore say that the wires have low resistance. However, in some appliances, for example, kettles or toasters, we want wires (more usually called heating elements) to become warm. The wires of a heating element are designed to have a high resistance so that as the current passes through them energy is transferred and the element heats up . We use this heating effect of current&nbsp; in many different ways in our homes.&nbsp;electricity
List some common appliances that make use of the heating effect of electricity.kettles, dishwashers, electric cookers, washing machines, electric fires, hairdryers.electricity
How does the heating effect work in a filament bulb?When current passes through the very thin wire (filament) of a traditional light bulb, it becomes very hot and glows (shines) white. The bulb is transferring electrical energy to heat and light energy.electricity
What is energy measured in and who is this named after?Joules<div><br></div><div>James Joule</div>work-and-power
In physics, what is work?In physics, work is the amount of energy transferred when a force moves an object. It must be in the direction of the force.work-and-power
Why is lifting doing work?When we lift objects, we are working because a force is working. Our lifting force is equal to the weight of the object. When putting weight into an equation for work done, we must first use the equation W (force) = m x g and because the&nbsp; gravitational potential on earth is 10, we are effectively multiplying the mass by 10.work-and-power
What is the equation for work done?Work done (J) = Force (N) x distance (m)work-and-power
What is the frequency of the a.c. mains electricity in the UK?50Hzelectricity
What is fossil fuel energy used for, how does it work, and list some advantages and disadvantages of it?Coal, oil and gas are extracted from beneath the Earth and burnt to release energy. This is easy and cheap, but the fuels are running out.<div><br></div><div>Advantages:</div><div><br></div><div>High energy density (lots of energy produced from small amount of fossil fuel).</div><div><br></div><div>Convenient to transfer to customers.</div><div><br></div><div>Reliable</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Fuel will run out, it's non-renewable.</div><div><br></div><div>Produces air pollution such as carbon dioxide.</div><div><br></div><div>Uses:</div><div><br></div><div>For heating:</div><div>Gas is bery easily piped to homes and businesses. This is a convenient way to deliver fuel. The gas is burned to make heat.</div><div><br></div><div>For Transport:</div><div>Oil can be turned into many fuels. Petrol and diesel for cars, busses lorries and trains can be made from oil. Kerosene can be made for airplanes.</div><div><br></div><div>For generating electrical energy:</div><div>Coal, oil or gas is burnt tp release the heat energy. The heat then heats water into high pressured steam which can turn a turbine and a generator, making electrical energy. Some powerstations even pipe the hot steam into nearby office buildings to heat them.</div>energy-resources-and-electricity-generation
What is nuclear fuel used for, how does it work, and list some advantages and disadvantages?<div>Nuclear fuel - energy from radioactive atoms.</div><div><br></div><div>Nuclear fuel can be used to generate huge amounts of electricity, for houses and other uses. Radioactive processes are used to make a lot of heat, which can be uses to heat water into high pressures steam, turning a turbine and then a generator which produces electrical energy.</div><div><br></div><div>Advantages:</div><div><br></div><div>Uses such small amounts of fuel so it is unlikely to run out.</div><div><br></div><div>Onty steam is released - no greenhouse gases.</div><div><br></div><div>Reliable and generate large amounts of electricity.</div><div><br></div><div>Disadvantgaes:</div><div><br></div><div>Non-renewable.</div><div><br></div><div>Decomissioning takes a long time and costs a lot of money.</div><div><br></div><div>Extremely hazardous waste products are made which will take thousands or millions of years to become safe.</div><div><br></div><div>There is a;ways a tiny risk of a meltdown, where hazardous radioactive materials can get into the environment, e.g Chernobyl.</div>energy-resources-and-electricity-generation
What does decomissioning mean?Decomissioning means to shut down the power station and remove the radioactive materials.energy-resources-and-electricity-generation
How does geothermal energy work, what is it used for, and what are some advantages and disadvantages of it?Geothermal energy - energy form the earth.<div><br></div><div>Geothermal energy is energy from the earth. Deep underground, the rocks are naturally very hot. By pumping cold water deep underground using pipes, we can use the hot water heated by the rocks either to make steam and generate electricity, or to heat and be pumped around peoples homes.<div><br></div><div>Advantages:</div><div><br></div><div>Renewable</div><div><br></div><div>No pollution, because nothing gets burned</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Very few places in the world where you can do this</div><div><br></div><div>Costs a lot of money to drill deep into the ground</div></div>energy-resources-and-electricity-generation
How does wind energy work, what is it used for, and list some advantages and disadvantages of it?Wind energy - energy from the wind.<div><br></div><div>Using wind turbines, we can turn the kinetic energy of the wind into electrical energy which we can use in our homes. This is 'wind energy'.<div><br></div><div>Wind turbines are only used to generate electrical energy. But they have social issues. Many people get upset when they are Built near their homes, because they thing they look ugly. Many people disagree.</div><div><br></div><div>Because wind turbines rely on the wind, they are not always reliable as it is not always windy.</div><div><br></div><div>Advantages:</div><div><br></div><div>Renewable</div><div><br></div><div>No pollution because nothing gets burned</div><div><br></div><div>Turbines are quite cheap and easy to build, so they can be used even in poor countries.</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Take up a lot of land</div><div><br></div><div>Turbines can be ugly and noisy</div><div><br></div><div>Not reliable, only works in windy conditions</div></div>energy-resources-and-electricity-generation
How does hydroelectric energy work, what is it used for, and list some advantages and disadvantages of it?Hydroelectric energy - energy from rivers.<div><br></div><div>The water flowing in a river has kinetic energy. We can turn this into electrical energy to use in our homes. We usually need to build a dam, and let water flow through it gradually.</div><div><br></div><div>As we let water through, the water runs past a turbine, turning it. This turns a generator, that converts the kinetic energy into electrical energy.</div><div><br></div><div>Advantages:</div><div><br></div><div>Renewable</div><div><br></div><div>No pollution, because nothing gets burned</div><div><br></div><div>We can store the water up high, and then whenever we need the enrgy we can let the water out</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Costs a lot of money to build a dam</div><div><br></div><div>The dam can ruin the local environment, because it changes where the water naturally flows. Some animals and plants may therefore die.</div>energy-resources-and-electricity-generation
How does tidal energy work, what are its uses and list some advantages and diasadvantages of it?Tidal barrage - energy from the sea.<div><br></div><div>In tidal energy, a large dam/barrage is built over a river estuary. As the tide comes in, a gate is opened. Before the tide goes out, the gate closes and traps the water. When the tide is out, the water is allowed to flow through a channel and turn a generator, converting the kinetic energy into electrical energy. Tidal barrages produce electrical energy, which can be supplied to houses as electricity.</div><div><br></div><div>Advantages:</div><div><br></div><div>Renewable</div><div><br></div><div>No pollution, because nothing gets burned</div><div><br></div><div>Predictable (but not reliable)</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Can only output energy twice per day when the tide is out</div><div><br></div><div>Harms the habitats of some wildlife, particularly wading birds.</div>energy-resources-and-electricity-generation
How does solar energy work, what is it used for, and list some advantages and disadvantages of it?Solar energy - energy from the sun.<div><br></div><div>The earth gets heat and light energy from the sun all the time. Cab we use it - yes we can. The sun's energy can either be:</div><div><br></div><div>1. Changed into electrical energy to use in our homes, using solar cells.</div><div><br></div><div>2. Or used to heat water for himes, using solar panels.</div><div><br></div><div>It is unlikely that you could ever run a whole house's energy needs on just solar panels - even on a sunny dau. But if everybody has them, the country would use a lot less gas to heat up water, and a lot less electricity from power stations.</div><div><br></div><div>Advantages:</div><div><br></div><div>Renewable</div><div><br></div><div>No pollution because nothing gets burned</div><div><br></div><div>Excellent in remote/isolated places like weather stations, satellites and remote villages</div><div><br></div><div>Disadvantages:</div><div><br></div><div>Solar cells and solar panels are expensive and take up a lot of space</div><div><br></div><div>Not reliable - only works if it's sunny</div>energy-resources-and-electricity-generation
What is a renewable energy source?A renewable enrgy source is one which can keep being replneished. It should, in theory, never run out.energy-resources-and-electricity-generation
What are the main things that us humans use energy for?"<b><ul><li><div>Heating<span style=""font-weight: 400;""> – we use resources to keep our buildings warm.</span><span style=""font-weight: 400;""><br><br></span></div></li><li><div>Transport<span style=""font-weight: 400;""> – we use energy to transport ourselves and our resources around the planet.</span><span style=""font-weight: 400;""><br><br></span></div></li></ul>Generating Electrical energy <span style=""font-weight: 400;"">– nearly everything we use needs electricity. We use most Earth’s energy to make electricity.</span></b>"energy-resources-and-electricity-generation
Suggest 2 advantages of using a circuit breaker to disconnect a circuit compared with using a fuse (pq).1. A circuit breaker can be reset whereas a fuse cannot.<div><br></div><div>2. A circuit breaker disconnects the circuit faster than a fuse.</div>electricity
"<div>(ii)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A
second drill is used with the extension lead. The power of this drill is 1200
W.</div>
<div>The instructions for using the extension lead include
the following information.</div>
<div>&nbsp;</div>
<table>
<tbody><tr>
<td>
<div>&nbsp;</div>
</td>
<td>
<div><b>When in use the lead may get hot:<br>
<br>
DO NOT go over the maximum power<br>
</b>•&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;lead wound inside the
case: 820 watts<br>
•&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;lead fully unwound outside
the case: 3100 watts</div>
</td>
</tr>
</tbody></table>
<div>&nbsp;</div>
<div>It would <b>not</b> be safe to use this drill with the
extension lead if the lead was left wound inside the plastic case.</div>
<div>Explain why.</div>""<div>(ii)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;power
is greater than 820 (W)</div>
<div><i>power is 1200 W is insufficient</i></div>
<div><b>1</b></div>
<div>the lead /cable / wire <u>will</u> overheat / get
(too) hot</div>
<div><i>accept lead / cable will melt</i></div>
<div><i>may overheat / get hot is insufficient</i></div>
<div><b>1</b></div>
<div>so there is a risk of fire</div>
<div><i>accept causing a fire</i></div><div><b>1</b></div>"electricity
"<div>(i)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
For safety reasons, it is important that the iron has an earth wire connected
to its outer metal case. Explain why.<br></div>""<div>)&nbsp;&nbsp;&nbsp;&nbsp;
(i)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if live wire touches case</div>
<div><i>accept if case becomes live</i></div>
<div><i>accept metal for case</i></div>
<div><b>2</b></div>
<div><b><br>
<br>
<br>
</b></div>
<div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
current flows to earth <b>or</b> ground<br>
<b>or </b>fuse melts <b>or </b>stops iron becoming live</div>
<div><i>accept electricity flows to earth</i></div>
<div><i>do <b>&nbsp;not</b> accept - you will get a shock</i></div>
<div><i>accept with <u>no earth</u> (wire) you would or could
get a shock for <b>1</b>mark</i></div>"electricity
Recall the equation for SHC."<img src=""paste-8615394e1677a611990ec7fa4e238733fdb49ee4.jpg"">"electricity
How can you tell if a graph shows a direct proportion and what does it mean?A direct proportion is shown by a straight line on a graph, passing through the origin. It means that if you double the x-value, the y-value will also be doubled.electricity
List the equation and rearrangements of it for kinetic energy."<img src=""paste-5cf4a68e9dd4db13e0bcecf409820a97bc729a95.jpg""><div><img src=""paste-a2bd70098db58bf0d028b2fa899bc2a41caa5612.jpg""><br></div><div><img src=""paste-eeacea32340d94fb6c02aeb8248e64eed9308f2a.jpg""><br></div>"work-and-power
Define power (2 ways).Power is the amount of energy that can be transferred every second.<div><br></div><div>Power is therefore the rate of change of energy.</div>work-and-power
Give the unites for the symbols in the KE equation and what they are measured in.V = Velocity (m/s)<div>m = Mass (kg)</div><div>KE = Kinetic energy (J)</div>work-and-power
"Complete one.&nbsp;<img src=""paste-8cd25f342c7cda5298b6ce1bb218c08493866f86.jpg"">""<img src=""paste-b483468ec4f509f4ca320da37fe4212378b634b4.jpg"">"work-and-power
Liat the equation for gravitational potential energy and its rearrangements."<img src=""paste-5b53ad3500fa772cc61174b4c0789d8427c5801f.png""><div><br></div><div>So:&nbsp;</div><div><br></div><div>E(p) = mgh</div><div><br></div><div>m = E(p)/gh</div><div><br></div><div>g = E(p)/mh</div><div><br></div><div>h = E(p)/mg</div><div><br></div><div>h = Heights (m)</div><div>g = Gravitational field strength (N/kg)</div><div>m = Mass (kg)</div><div>E(p) = Gravitational potential energy (J)</div>"work-and-power
What is GPE directly proportional to?On earth, gravitational field strength is always constant. So, if mass is constant, then GPE is directly proportional to height (if you move the same object to different heights this will be directly proportional). Similarly, if height is constant, then GPE is directly proportional to mass (lifting something onto a shelf is harder to do if it has more weight (W = mg)).work-and-power
"Complete one.&nbsp;<img src=""paste-b498c87c1a12ead1359f6cf6036675c45c163412.jpg"">""<img src=""paste-d9e4adb8c6fb3d83925e42c385317cb372e1715f.jpg"">"work-and-power
How much GPE does an object have before we do work on it?0Jwork-and-power
Explain the energy transfers in weight-lifting.In weightlifting, the weightlifter has used some chemical energy to do the work. We know that energy is conserved so some energy has been transferred to heat in the weightlifter's body. The remainder has been transferred to the weight (he is lifting) because he has increased its height in the gravitational field of earth. The energy that the weight has gained is called gravitational potential energy or GPE.work-and-power
Explain the energy transferred when a weight is dropped.GPE stored by the weight is being transferred to other stores as the weight falls. The weight accelerates because of the force of gravity acting on it, so it gains kinetic energy. When it reaches the gorund, all the initial GPE is transferred to kinetic energy. When it hits the hround all th emovement energy is then transferred to other stores, mainly heat and sound.work-and-power
"Complete 1.&nbsp;<img src=""paste-ba8325e4f79d9e5dbae070f7a1a5904ec334e1c0.jpg"">"Answer to both = 10Jwork-and-power
What is energy?Energy is the ability to do workwork-and-power
List the equation for work done and the units.W = F X d<div><br></div><div>Work done, W (joules) = Force, F (newtons) x distance moved, d (metres).</div><div><br></div><div>If the force is measured in newtons (N) and the distance through which the force is applied is measured in metres (m) then the work done will be in joules.</div><div><br></div><div>Work done is equal to the amount of energy transferred.</div><div><br></div><div>Consequently, 1J of work done is transferred when a force of 1N is applied through a distance of 1m in the direction of the force.</div>work-and-power
What is work done also?Energy.work-and-power
How is work done?When a force moves an object through a distance, work is done and energy is transferred.work-and-power
Define power.Power is the rate of transfer of energy.work-and-power
What is a watt and list the equation for power?The watt is the rate of transfer or conversion of energy of one joule per second (1J/s).<div><br></div><div>P = W/t</div><div>t = W/P</div><div>W = Pt</div><div><br></div><div>W can also be E</div><div><br></div><div>(P = E/t etc)</div>work-and-power
Define momentum.Momentum (p) is a measure of how difficult an object is to stop.forces-year10
List the equation for momentum, it's rearrangements and units.momentum = mass x velocity<div><br></div><div>p = mv</div><div><br></div><div>m = p/v</div><div><br></div><div>v = p/m</div><div><br></div><div>m = mass = kg</div><div><br></div><div>v = velocity = m/s</div><div><br></div><div>p = momentum = kgm/s</div>forces-year10
Explain the law of oncservation of momentum.The law of conservation of momentum states thats:<div><br></div><div>In a closed system with no external forces acting, the totsl momentum before a collision (or explosion) is the same as the total momentum after the collision.</div><div><br></div><div><br></div><div><br></div><div>This basically states that:</div><div><br></div><div>momentum before the collison = momentum after the collision.</div>forces-year10
What is momentum directly proportional to?Momentum is directly proportional to:<div><br></div><div>Mass</div><div>Velocity</div>forces-year10
How many mph is 13m/s?30forces-year10
Is momentum scalar or vector?Vector - it has a size and direction.forces-year10
What is the voltage of the live, neutral and earth wire respectively?Live - 230V<div>Neutral - 0V</div><div>Earth - 0V</div>electricity
What is significant about the total resistance of two resistors in parallel.The total resistance of two resistors in parallel is less than the resistance of thje smallest inddividual resistor.electricity
"Complete 1.<img src=""paste-d392b95c9e9890a1d8d53e0014e98082ceaa02d5.jpg"">""<img src=""paste-ced4542330c14b18c1f4b2088c187c99a0a67a1e.jpg"">"forces-year10
List 2 different equations for change in momentum and the units."<img src=""paste-cf4991c3969358bcfa34c55d45eef7636aabb8bb.jpg""><div><br></div><div>or F =&nbsp;<img src=""paste-656865d31dafb46e8ce98d57c10b44cdddc71b62.jpg""></div><div><br></div><div><br></div><div>F = Force (N)</div><div>m = Mass (kg)</div><div>v = Velocity (m/s)</div><div>t = Time (s)</div><div><br></div><div><br></div><div>Unit for change in momentum = F</div>"forces-year10
Explain Isaac Newton's discoveries in terms of change in momentum.The relationship F=ma was first discussed by Isaac Newton. A more precise statement of his discovery would be that 'when an unbalanced force acts on an object it causes a change in the momentum of the object in the direction of the unbalanced force. Newton also discovered that the rate of change of momentum of an object is proportional to the force applied to that object. This means that if you double the force acting on an object, its momentum will change twice as quickly.forces-year10
Explain what steep roads often have to reduce injuries from car crashes.Steep roads often have lanes filled with deep, soft sand. The soft sand slows heavy lorries that are out of contorl slowly - by making time, t, for the lorry to stop longer, the force, F, slowing the lorry is smaller and the driver is less likely to suffer serious injury.forces-year10
Explain how crumple zones work.Crumple zones absorb the kinetic energy of an impact by destroying the car and the crumple zones also increase the impact time. The 'cell' (area where passengers sit) is more rigid and not destroyed to crumple.<div><br></div><div>Cars are now designed with various safety features that increase the time over which the car's momentum changes in an accident. Cars have a rigid passenger cell or compartment with crumple zones in front and behind. The crumple zones collapse during a collision and increase the time during which the car is decellerating.</div>forces-year10
How do seatbelts work?"<b><div><span style=""font-weight: 400;"">Seatbelts stretch ‘plastically’ when a large force is applied. This increases the time taken to slow the passenger.&nbsp;</span><span style=""font-weight: 400;"">Also prevents the passenger from flying through the windshield or dashboard.</span></div></b><br><div>Crumple zones only work if the passengers are wearing seat belts so that the reduced deceleration applies to their bodies too. Without seat belts, the passengers will continue moving forward until they come into contact with some part of the car or with a passenger in front.&nbsp;</div>"forces-year10
How do airbags work?"<b><span style=""font-weight: 400;"">Airbags inflate rapidly, then deflate when hit. Provides a soft cushion which increases the time taken to slow down.</span></b>"forces-year10
What holds our solar system together?Gravitational forces.astrophysics
What do gravitational forces in the solar system cause?The planets, assteroids, and comets to orbit the sun, and moons and artificial satellites to orbit the planets.astrophysics
What do planets, comets, moons and satellites travel around?Planets = Sun<div>Comets = Sun</div><div>Moons = Planets</div><div>Satellites = Planets</div>astrophysics
What did Newton's theory of gravity explain and what is it?For planets and comets to travel around the sun, and moons and satellites to travel around the planets, there must be forces applied to them. In 1687, Isaac Newton suggested where these forces come from, when suggesting his theory of gravity to explain these movements.<div><br></div><div>Newton suggested that between any two objects there is always a force of attraction. This attraction is due to the masses of the objects. He called this force gravitational force.</div><div><br></div><div>He suggested that the size of the gravitational force depends on the:</div><div><br></div><div>1. The masses of the two objects.</div><div>2. The distance between the masses.</div><div><br></div><div>The greater the masses of the two objects, the stronger the attractive force between them.</div><div>If the distance between the masses is increased the forces between them decrease.</div>astrophysics
What do gravitational forces obey?Gravitational forces obey an inverse square law - that is, if the distance between the masses is doubled, the forces between them are quartered; if the distance between them is trebled, the forces become one ninth of what they were.astrophysics
What is the sun and what is the suns function in the Solar System?Our sun is massive. It contains over 99% of the mass of the Solar System. It is the gravitational attraction between this mass and each of the planets that holds the Solar System together and causes the planets to follow their curved paths.astrophysics
Explain the force of attraction felt by planets close and far away from the sun.Those planets that are closest to the Sun feel the greatest attraction and so follow the most curved paths. Plaets that are the furthest from the Sun feel the weakest pull and follow the least curved path.astrophysics
What is a satellite?A satellite is an object that orbits a planet.astrophysics
What are natural satellites called?Moons.astrophysics
Explain moons in terms of the moon on the earth and other moons in our solar system.Natural satellites are called moons. The Earth has just one moon. It is the fifth largest moon in our solar system, approximately 340,000km from Earth, and takes just over 27 days to complete one orbit. Although we call our moon 'The Moon', it is not unique. Many planets have moons. Some have more than one. For example, Mars has two moons whule Jupiter and Saturn have more than 60 each. All moons have circular orbits because of the gravitational forces between them and their planet.astrophysics
Explain artificial satellites and in particular their uses.Since the ate 1950', humans have been able to launch, and put into orbit around the earth, artifical satellites. Artificial satellites are extremely useful. Some satellites are put into a very high orbit above the Earth and are used to help us communicate ober large distances; for example, for international phone calls or video links, the internet ans so on. Some satellites are put into a much lower orbit and are used to monitor in detail the Earth's surface, such as the temperature of the world's oceans or the progress of forest fires.astrophysics
What are comets?Comets are large rock-like pieces of ice that orbit the sun. They have very elliptical orbits which at ties take them very close to the sun. At other times, they travel close to the very edge of our solar system.astrophysics
Compare the orbits of planets and comets."<img src=""paste-34bba11b753ddd332eecf010e85ba6a8cdad2633.jpg"">&nbsp;= PLANET ORBIT<div><br></div><div><img src=""paste-f593e24aa480216b6d70adb7a0bec768883201ec.jpg"">&nbsp;= COMET ORBIT<br></div>"astrophysics
What is gravitational field strength and what is the gravitational field strength of the Earth and Moon?Gravitational field strength is the strength of gravity on a planet or moon, and it is given the symbol 'g'.&nbsp;<div><br></div><div>The gravitational field strentgh on the Earth is approximately 10N/kg while on the Moon it is approximately 1.6N/kg.</div>astrophysics
What factors affect gravitational field strength and how?Different planets have different masses and different radii - both of these will affect their gravitational field strengths.<div><br></div><div>The larger the mass of a planet, the greater its gravitational field strength.</div><div><br></div><div>The larger the radius of a planet, the smaller the gravitational field strength at its surface.</div>astrophysics
Compare the gravitational field strength of the moon and earth and what this means.On the Moon, the gravitational field strength is only one sixth that of the Earth's. This means that on the Moon you would weigh six times less because W = m x G. If, however, you visited Jupiter, you would weight almost 2/5 times more.astrophysics
What is gravitational field strength measured in?N/kg.astrophysics
Explain how the orbital speeds of satellites vary greatly.The orbital speeds of satellits vary greatly depending on the tasks they are performing. For example, communication satellites are put in high orbits and travel at approximately 3km/s, while those observing the whole surface of the Earth are put itno low polar orbits with seppds of about 8km/s.astrophysics
Recall the equation for orbital speed."<img src=""paste-4af83ee23360cd1c37a1d6502d7dd3b5e1a3ea20.jpg"">"astrophysics
How is the radius of an orbit (orbital radius) calcualted?The radius of the orbit is measured from the centre fo the Earth - that is, it is the radius of the earth plus the height of the orbit above the Earth's surface.astrophysics
What is the equation for weight?Weight = mass x gravitational field strength<div><br></div><div>W = mg</div><div><br></div><div>W = Newtons (N)</div><div><br></div><div>m = mass (kg)</div><div><br></div><div>g = gravitational field strength (N/kg)</div>astrophysics
What does the strength of gravity on the surface of the planet depend on?The mass of the planet and the radius of the planet (therefore big planets don't always have the largest gravitational field strength).astrophysics
Compare the gravitational field strength of Saturn and the Earth and explain this.Although being a lot bigger/having a larger mass than the Earth, Saturn has a weaker gravitational field stength on the surface of the planet. This is because, the radius of Saturn is a lot larger than the radius of the Earth. Therefore, you can't feel the gravitational field strength as much on Saturn as you can on the Earth.astrophysics
Why does a comet travel fastest when closest to the sun?This is because, as the comet gets closer to the suns core, it loses a gravitartional potential energy store, Therefore, it gains a kinetic energy store as energy is conserved. The more kinetic energy it has, the faster it will move.<div><br></div><div>Furthermore, gravitational field strength varies with distance. The closer you get to a star or planet, the stronger the gravitational force is. The stronger the force, the larger the instantaneous velocity needed to balance it. So the closer to the Sun the comet gets, the daster it needs to go to remain in orbit (this is the same for any object in orbit).</div>astrophysics
Where is our solar system?Our solar system is in the Mily Way galaxy.astrophysics
What is a galaxy?A galaxy is a large collection of billions of stars.astrophysics
What is the universe?The universe is a large collection of billions of galaxies.astrophysics
Explain all the things that gravitational force causes.Gravitational forces:<div><br></div><div>- causes moons to orbit planets.</div><div>- causes the planets to orbit the sun.</div><div>- causes artificial satellites to orbit the Earth.</div><div>- causes comets to orbit the sun.</div>astrophysics
What is the Solar System?The Solar System is all the stuff that orbits our Sun. This includes things like:<div><br></div><div>Planets</div><div>Dwarf Planets</div><div>Moons</div><div>Artificial Satellites</div><div>Asteroids</div><div>Comets</div>astrophysics
What are planets?Planets - these are large objects that orbit a star. The eight planets in our Solar System are, in order (from the sun outwards): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.astrophysics
What are dwarf planets?Dwarf planets are planet-like objects that aren't big enough to be planets, such as Pluto.astrophysics
What are moons?Moons orbit planets with almost circular orbits. They're a type of natural satellite.astrophysics
What are artificial satellites?Artificial satellites (ones humans have built) are ones that usually orbit the Earth in fairly circular orbits.astrophysics
What are asteroids?Asteroids are lumps of rock and metals that orbit the Sun. They're usually found in the asteroid belt.astrophysics
Define comets.Comets are lumps of ice and dust that orbit the sun. Their orbits are usually highly elliptical - some travel from near to the sun to the outskirts of our Solar System.astrophysics
Explain in detaol how gravity provides the force that creates orbits.The planets move around the Sun in almost circuar orbits. An object in a circular orbit at a constant speed is constantly acceelrating (this is just a fact). The force causing this is a centripetal force. It acts towards the centre of the circle. This force would cause the object to just fall towards whatever it was orbitting, but as the object is already moving, it just causes it to change its direction. The object keeps accelerating towards what it's orbiting, but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle. The force that makes this happen is provided by the gravitational force (gravity) between the planet and the Sun (or between the planet and its satellites).astrophysics
How do you get from m3 to cm3?multiply by 1,000,000energy-transfers
Give an example of how energy is wasted in cars.We provide our cars with an energy store (the tanks of petrol). We want energy from this store to be transferred to the kinetic energy of the moving car, and to gravitational energy if we are driving ip a hill - both transfers are useful. Heating will also transfer thermal energy to the surroundings, sound will radiate energy to the surroundings and friction between moving parts abd tge air will cause mechanical work to be done, making things get hot and therefore transferring thermal energy to the surroundings. These are examples of chemical energy stored in the fuel being transferred to unwanted energy stores.energy-transfers
What is an energy transfer diagram?We use different ways to show how energy is transferred. Energy transfer diagrams show the energy input (contribution), the energy transfer process, and the energy output (production). The system may be a very simple mone with just one main energy transfer rpocess taking place.energy-transfers
What is a sankey diagram?Sankey diagrams are a simpler and clearer way of showing what happens to an energy input into a system. The energy flow is shown by arrows whose width is proportional to the amount of energy involved. Wide arrows show large energy flows and narrow arrows show small energy flows.energy-transfers
What do real energy systems always have?Real energy systems always have an unwanted energy output so can never have 100% efficiency.energy-transfers
Recall the equation for efficiency."<img src=""paste-704887be5b070726e5dd24800a6172b584a4e456.jpg""><div><br></div><div>(you can multiply this number by 100 (x100) to get this as a percentage and then express the efficiency as a percentage if you want but this is optional).</div>"energy-transfers
What is conduction?Conduction is the transfer of heat from hot to cold through a solid material by the collisions of vibrating particles and by the movement of free electrons in metals.energy-transfers
Where is thermal energy always transferred?Thermal energy is always transferred from a place that is hotter to one that is colder.energy-transfers
Explain the process of energy transfer by conduction un terms of the behaviour of the tiny particles that make up all matter.The process of transfer by conduction is explained in terms of the behaviour of the tiny particles that make up all matter. In a hot part of a substance, these particles have more kinetic energy. The more energetic particles transfer some of their kinetic energy store to particles near them mechanically. These therefore gain kinetic energy and then pass kinetic energy on to particles near them. The enrgy transfer goes on throughout the substance. This process takes place in all materials.energy-transfers
Why does conduction take place much more rapidly in metals?In metals, the process of conduction takes place much more rapidly, because metals have free electrons that can move easily through the structure of the metal, making the transfer of energy happen faster.energy-transfers
Explain conduction when heatin metal and wooden skewers over the barbecue.The metal skewer over the burning charcoal becomes hot and the thermal energy is transferred along the skewer by conduction. In metals, this takes place quite rapidlt and soon the handle end is almost as hot as the ned over the fire. Metals are good thermal conductors. If you use skewers with wooden handles, you can hold the wooden ends much more comfortably, because wood does not conduct thermal enrgy very well. Wood is an example of a good thermal insulator.energy-transfers
What is convection?Convection is the transfer of thermal energy through fluids (liquids and gasses) by the upward movement of warmer, less dense, regions of fluid.energy-transfers
Explain how a convection current forms when potassium manganate is added to water to demonstrate convection currents.In this demonstration of convection currents in water, the water is heated just under the purple crystal and the crystal colours the water as it dissolves, which lets you see the movement in the water. The heated water expands and becomes less dense than the colder surroundig water, so it floats up to the top of the glass beaker. Colder water sinks to take its place, and is then heated too. At the top, the warm water starts to cool, becomes more dense again and will begin to sin, so a circulating current is set up in the water. This is called a convection current.energy-transfers
Explain how onvection currents work in convection heaters.Convection occurs in any fluid substance - that is, in things that can flow, such as liquids and gases. Convector heaters heat air, which then floats out of the top of the heter to the top of the room, Cold air is drawn in at the bottom and this is heated. In this way, thermal energy is eventually transferred to all parts of the room.energy-transfers
Explain how convection works in many cooking ovens.In many cooking ovens, the heating element is placed at the bottom of the oven. It heats the air near to it, and this rises by convection. The top of the oven is generally warmer than the bottom, so you can cook foods at different temperatures. However, many modern ovens are fan ovens, where hot air is blown into the oven and provides an even temperature throughout the oven.energy-transfers
Explain air and water in terms of convection and conduction, and explain how they are as conductors makes them useful for many things.Air and water both allow thermal energy transfer to take place by convection as they are both fluids, but neither are good thermal conductors (they are insulators). This insulating property of both water and air is put to good use in situations where they are not abel to circulate easily. For example, woolen clothing keeps you warm because air gets trapped in the fibres. The trapped air is heated by your body and forms a warm insulating layer that helps to stop you losing heat. In the same way, a wetsuit keeps a diver warm because a thin layer of water is trapped next to the diver's skin.energy-transfers
Give 2 examples where convection currents are responsible for everyday events.1. On-shore and off-shore breezes, alko known as sea breezes and land breezes.<div><br></div><div>2. Another example is cinvection currents within the very tall 'thunder' clouds that are responsible for the buil-up of charge at the cloud base, resulting in lightning strikes.</div>energy-transfers
Explain how animals keep warm.Animals keep warm in different ways. You may have noticed birds fluffing ip their feathers on cold days in winter. This increases the thickness of the trapped air layer around their bodies, so reducing heat loss by conduction. Some birds, like penguins, will move close together for warmth. Other animals will curl into small balls. This cuts down heat loss by making the surface area of their bodies exposed to the cold as small as possible.energy-transfers
Explain hyperthermia and how people who are suffering from the effects of cold are treated.When people do lose body heat at too great a rate, they may become hypothermic, which means their body temperature starts to fall. If the heat loss is not significantly reduced, the condition is potentially fatal. When people are rescued from mountains suffering from the effects of cold, they are usually wrapped in thin, highly reflective blankets. The interior reflective surface reflects heat back to their bodies while the outer reflective surface is a poor radiator of heat. Marathon runners are often covered in these blankets at the end of the race to keep them warm when their energy reserves are low.energy-transfers
Explain the obvious method of cutting down heat loss.The obvious method of cutting down heat kiss from the body us to wer clothes. Clothes that trap air around the body provide insulation, because trapped air cannot circulate and is a very poor conductor. A large proportion oof body heat is lost from the head, so hats are the human equivalent of loft insulation.energy-transfers
Explain what wind can cause and how it causes this.Wind can cause rapid heat loss from the body. It does this by forced convection - that is, making air circulate close to the body surface. It may also cause sweat to evaporate from the skin more quickly, causing rapid cooling. (The purpose of sweat is to help the body to lose heat by evaporation, but, if it happens because of strong wind on a cold day, the effect can be life threatening). These cooling effects of wind contrivute to what is called the wind-chill factor. To reduce the wind-chill effect, a piece od wind-proof outer clothing should be worn.energy-transfers
What is thermal radiation?Thermal radiation is the transfer of energy by infrared (IR) waves.energy-transfers
Explain how thermal imaging works.The army and the emergency services use special cameras, called thermal imaging cameras, that can detect objects giving out IR waves. These cameras show images of people because of the thermal radiation from their bodies, even when there is not enough visible light to actually see them. Thermal imaging is also an important tool in the diagnosis of certain illnesses.energy-transfers
Explain how you will feel the effect of turning on a bathroom heater almost instantly.This is because, in this exmample, thermal energy is travelling in the form of waves, like visible light. Heat waves are called infrared (IR) waves or IR radiation.energy-transfers
What is the speed of light?3 x 10 to the power of 8 m/s.energy-transfers
Why is it improtant that thermal energy can travel via infrared radiation, without the need for matter?Because otherwise, we would not recieve heat, as well as light, from the Sun.energy-transfers
What is a good reflector of IR also?What is a poor radiator of IR also?Yesenergy-resources-and-electricity-generation
What else (other than how a material feels to the touch and colour) affects the amount and type of the enrgy radiated by a hot objected?Temperature - how hot something is. Not only does the amount of energy radiated per second increase significantly with temperature, but the nature of the EM waves also changes. At a low temperature, most of the radiated energy is in the form of infrared waves (invisible to the human eye). As the temperature of a metal object increases, it starts to radiate in the visible spectrum as well. Things that do not burn will start to glow a dull red. As the temperature rises further, the colour changes through the visible spectrum. For example, a tungsten filament glows white hot when it reaches around 3,000 degrees celsius.energy-resources-and-electricity-generation
Explain how roof/loft insulation works.Roof/loft insulation in modern houses uses similar panels to those used in the wall cavities, trapping a thick layer of air. This akes advantage of the poor conduction property of aur, while also preventing convection currents circulating. Again, reflective foil is usually used to reduce radiation heat loss. All these features mean that heat stays within your house for longer, which saves money, keeps you warm and reduces global warming.energy-resources-and-electricity-generation
Explain thermostats, computer control systems and reducing draughts from doors and windows.These things don't relate directly to the mechanisms of thermal energy transfer. Thermostats and computer control systems for central heating can further reduce the heating needs of a house. They stop rooms being heated too much by switching off the heat when a certain temperature is reached. Another important energy-saving measure is the reduction or elimination of draughts (air currents) from poorly fitting doors and windows.energy-resources-and-electricity-generation
What does help reducing heat transfer in houses help with?- Saves money.<div>- Keeps house warm.</div><div>- Reduces global warming.</div>energy-resources-and-electricity-generation
Explain how double-glazed windows work.Glass is a poor thermal cinductor but is used in thin layers. To improve the insulating properties, two layers of glass are used to trap a layer of air. The thickness of this layer is important. If it is too thin, then the insulation effect will be reduced, but if it is too thick, then convection currents wil be able to circulate and carry heat from the hotter surface to the colder one. In very cold countries, triple glazing is used. Modern double glazing uses special glass to increase the greenhouse effect (heat radiation from the sun can get in but radiation from inside the house is mainly reflected back again). Double glazed windows reduce conduction, and, if placed close enough together, convection currents. In between the panes is usually argon, which is a low pressure gas and a poor conductor of heat.energy-resources-and-electricity-generation
Explain how carpets work.A carpet is a floor covering made from thick woven fabric that helps to insulate the surroundings. Carpets insulate the floor and prevent draft from floorboards to keep warm air inside it. Carpets reduce conduction.energy-resources-and-electricity-generation
Explain how hot water tank jackets work.Hot water tank jackets put an insulator on your hot water tank so it doesn't lose heat. Fitting a hot water tank jacket with insulate the tank and therefore the temperature in the water tank will stay warmer for longer. It is reducing heat loss by conduction.energy-resources-and-electricity-generation
Explain how cavity wall insulation prevents conduction.In cavity insulation, the wall is made with layers of different materials. The outer layer is made with bricks - these have quite good insulating properties, are strong and will survive bad weather conditions. The inner layer is built with thermal bricks with very good insulation properties - they are also light, relatively cheap and quick to worth with. The two layers of brcik are separated by an excellent thermal insulator in the from of an air cavity gap. This prevents conduction.&nbsp;energy-resources-and-electricity-generation
Explain how cavity wall insulation prevents convection and infrared radiation.The walls also stop heat being lost by convection. The cavity or gap between the two walls is wide enough for convection currents to circulate. So, to stop convection currents, the gap in modern houses&nbsp; is filled with insulating panels ade of glass fibre matting. This is a lightweight, poor conductor that traps lots of air. The panels are usually surfaced with thin aluminium foil. This highly reflective surface reflects heat in the form of infrared radiation. Therefore, cavity wall insulation also prevents convection and infrsred radiation.energy-resources-and-electricity-generation
Define energy.Energy is the ability to do work.<div><br></div><div>Energy makes things happen. Where there is energy in a system, changes can occure, which sees energy transfer from one form to another.</div>energy-resources-and-electricity-generation
What is a system?A system is any object (or objects) where energy can change from one form to another.energy-resources-and-electricity-generation
What happens during energy transfers?Suring energy transfers, some energy is always converted to wasted energy.energy-resources-and-electricity-generation
Explain the enrgy transfers in a pendulum.The store fo energy at the ends of the pendulum swing is gravitational potential energy. The store of energy at the bottom of the swing is kinetic energy. The energy is being transferred mechanically from gravitational potential energy to kinetic energy. The kinetic energy is wasted because the pendulum eventually stops swinging. This means that some energy has been wasted. Kinetic energy is being transferred from the pendulum to the air particles. In other words, the wasted energy is dissipating into the surroundings. This is why the pendulum is slowing down and eventually stops. The pendulum is also hitting the air around it and the air resistance is slowing down the pendulum.energy-resources-and-electricity-generation
State the law of conservation of energy.The law of conservation of energy states that:<div><br></div><div>Energy cannot be created or destroyed. It can only be transferred from one store to another.</div>energy-resources-and-electricity-generation
Define efficiency.Efficiency is the proportion of energy from a transfer that becomes useful.energy-resources-and-electricity-generation
Show the efficiency equation triangle.&nbsp;"<img src=""paste-4616445d9635a2d3fa33a09f02823db50eee8d67.jpg"">"energy-resources-and-electricity-generation
Explain what happens when rickets are attached by wax to a copper rod, and the copper rod is heated at one end.When rickets are attached by wax to a copper rod, the rickets fall off from the rod one by one from nearest to the heat source, to farthest from the heat source. This is because, heat will always go from hot to cold. Copper is the best conductor of heat out of itself, aluminium, steel and brass. Many wires and pipes are ade out of copper because of this, and also because copper is quite unreactive with water and air, so won't corrode.energy-resources-and-electricity-generation
Why does metal feel cold?Metal is a good conductor of heat. When you touch metal, the metal feels cold. This is because, the metal conducts the heat away from your hand. It conducts it away and into the surroundings. Therefore, your hand now feels cold.energy-resources-and-electricity-generation
Why do you feel warm when you go to bed at night?When you go to bed at night, you feel warm. This is because, your bed sheets and duvet are good insulators of heat, as they are made of good insulating materilas such as cotton. This means, that when you touch it, it takes the heat but doesn't spread it away into the surroundings. Therefore, you feel warmer.energy-resources-and-electricity-generation
Why does an ice cube melt quicker on a metal tray than a plastic tray?The ice cube melted quicker on the metal tray than the plastic tray because metal is a better conductor of heat. Therefore, it brings in more heat from the surroundings at a quicker rate than the plastic tray (it brings heat in because hat always moves from hot to cold). Therefore, the heat it conducts melts the ice cube quicker.energy-resources-and-electricity-generation
What happens to infrared radiation emitted as the temperature of an object increases?The hotter an object is, the more infrared radiation it will emit per second.energy-resources-and-electricity-generation
Which surfaces are the best absorbers, best emitters and worst reflectors of infrared radiation?Matt black surfaces are the best absorbers, best emitters, and worst reflectors of infrared radiation.energy-resources-and-electricity-generation
Which surfaces are the worst&nbsp;absorbers, worst emitters and best reflectors of infrared radiation?White sjiny surfaces are the worst absorbers, worst emitters and best reflectors of infrared radiation.energy-resources-and-electricity-generation
Explain the relationship between temperature of an object and intensity of infrared emission.The higher the temperature of an object, the higher the intensity of infrared emission.energy-resources-and-electricity-generation
What is the unit for infrared emission intensity?Watts per square metre (W/m^2).energy-resources-and-electricity-generation
Explain what happens if an object absorbs more, less or equal infrared radiation than it emits.Same rate = Stays at constant temperature.<div>More than emits = Hotter.</div><div>Less than it emits = Colder.</div>energy-resources-and-electricity-generation
Explain why fluids become less dense when heated.When particles in a fluid are heated, they move faster with more energy. The distance berween the particles will therefore increase. The overall volume of the fluid will increase. The number of particles stay the same when heated because of the law of conservation of gas.&nbsp; The mass of the fluid will stay the same because not more particles will have been created or destroyed. The overall density of the fluid will decrease because the particles are further apart from one another.energy-resources-and-electricity-generation
Explain how lava lamps work.In a lava lamp, there is a lamp that heats the wax up. The wax is travelling theough oil. When the wax is heated up, it becomes less dense then oil. Therefore, it rises. When the wax reaches the top of the lava lamp, it is still less dense than the oil. Hpwever, it then starts to cool down and therefore soon becomes more dense then the oil. Consequently, it sinks back down to the bottom of the lamp, eventually being heated agaun and making a constant cycle.energy-resources-and-electricity-generation
Why can't convection happen in a vacuum?Because there are no particles in a vacuum. Particles are needed for convection.energy-resources-and-electricity-generation
Why can't convection happen in solids?Convection cannot happen in solids because convection happens when fluids become less dense. They become less dense because the particles in them become further apart from one another. However, in solids, the particles are in fixed positions and cannot freely move, unlike in fluids.energy-resources-and-electricity-generation
What does the total energy in a closed system have?No net change.energy-resources-and-electricity-generation
What is a kinetic energy store?Kinetic - anything moving has energy in its kinetic energy store (e.g moving car).energy-resources-and-electricity-generation
What is a thermal energy store?Thermal - any object - the hotter it is, the more energy it has in this store (e.g fire).energy-resources-and-electricity-generation
What is a chemical energy store?Chemical - anything that can release energy by a chemical reaction (e.g food).energy-resources-and-electricity-generation
What is a gravitational potential energy store?Gravitational Potential - anything in a gravitational field (anything that can fal) (e.g book on a shelf).energy-resources-and-electricity-generation
What is an elastic potential energy store?Elastic potential - anything stretched (e.g stretched spring).energy-resources-and-electricity-generation
What is an electrostatic energy store?Electrostatic - two charges that attract or repel eachother (e.g rubbing a balloon against your head).energy-resources-and-electricity-generation
What is a magnetic energy store?Magnetic - two magnets that attract or repel eachother (e.g a magnet).energy-resources-and-electricity-generation
What is a nuclear energy store?Nuclear - atomic nuclei release energy from this store in nuclear reactions (e.g in a nucleus).energy-resources-and-electricity-generation
What is a closed system?A closed system is just a system (a collection of objects) that can be treated completely on its own and where there is no net change in the system's total energy.energy-resources-and-electricity-generation
What is transferring energy mechanically?Mechanically - a force acting on an object (e.g pushing, stretching, squashing).energy-resources-and-electricity-generation
What is transferring energy electrically?Electrically - a charge doing work (e.g charges moving round a circuit).energy-resources-and-electricity-generation
What is transferring energy by heating?By Heating - energy transferred from a hotter object to a colder objects (e.g heating a pan on a hob).energy-resources-and-electricity-generation
What is transferring energy by radiation.By Radiation - energy transferred by waves (e.g energy from the Sun reaching Earth by light).energy-resources-and-electricity-generation
Explain the energy transfers in a ball rolling up a slope.The ball does work against the gravitational force, so energy is transferred mechanically from the kinetic energy sotre of the ball to its gravitational potential energy store.energy-resources-and-electricity-generation
Explain the energy transfers in a bat hitting a ball.The bat has energy in its kinetic energy store. Some of this is transferred mechanically to the ball's kinetic energy store. Some energy is also transferred mechanically to the thermal energy stores of the bat and the ball (and to the surroundings by heating). The rest is carried away by sound.energy-resources-and-electricity-generation
Explain the energy transfers in a rock dropped from a cliff.Assuming there's no air resistance, gravity does work on the rock, so the rock constantly accelerates towards the ground. Energy is transferred mechanically from the rock's gravitational potential energy store to its kinetic energy store.energy-resources-and-electricity-generation
Explain the energy transfers in a car slowing down (without braking).Energy in the kinetic energy stores of the car is transferred mechanically (due to friction between the tyres and road), and then by heating, to the thermal ebergy stores of the car and road.energy-resources-and-electricity-generation
Explain the energy transfers in a kettle boiling water.Energy is transferred electrically from the mains to the heating element of the kettle, and then by heating to the thermal energy store of the water.energy-resources-and-electricity-generation
Why can the effiiciency of a device never be equal to or higher than 1 (or 100%)?Because some energy is always wasted.energy-resources-and-electricity-generation
Explain the density of solids, liquids and gasses.Solids, liquids and gasses have different properties and characteristics. One such characteristic is density. Solids are often very dense - that is, they have a high mass for a certain volume. Liquids are often less dense than solids, and gasses have very low densities.solids-liquids-and-gasses
Recall the equation for density and its rearrangements."<img src=""paste-9f98e1896da882a77a0b75f5ab6ce3a4857797ee.jpg""><div><br></div><div>m = mass (kg)</div><div>V = volume (m^3)</div><div>p = density (kgm^3</div><div><br></div><div>The units for density depend on the units for mass and volume. If mass is measured in kilograms and volume in cubic metres, the units for density are kilograms per cubic metre (kg/m^3). Density can also be measured in grams per cubic cenimtre (g/cm^3).</div>"solids-liquids-and-gasses
Explain the basic idea of pressure using examples of a pin/thumb pushing into wood and a sharp/blunt knife.You can push a drawing pin into a piece of wood quite easily, but you cannot make a hole in the wood with your thumb, no matter how hard you push. The small point of the drawing pin concentrates all your pushing force into a tiny area, so the pin goes into into the wood easily. Similarly, it is easier to cut things with a sharp knife than a blunt one, because with a sharp knife, all the force is concentrated into a much smaller area.solids-liquids-and-gasses
Define pressure.Pressure is defined as the force per unit area.solids-liquids-and-gasses
State the equation for pressure."<img src=""paste-7d4ff59927d159b8d1fe2bd29798980f8cd31dd2.jpg""><div><br></div><div>F = Force (N).</div><div>A = Area (m^2)</div><div>p = Pressure (Pa)</div>"solids-liquids-and-gasses
What is the unit for pressure and what is 1 of the unit equivalent to?Pascals (Pa).<div><br></div><div>1 Pa is equivalent to 1 N/m^2.</div>solids-liquids-and-gasses
Explain some times where high pressure and low pressure is needed and how things are adapted for this.Some machines, including cutting tools like scissors, bolt cutter and knives, need to exert a high pressure to work well. In other applications, a low pressure is important. Tractors and other vehicles designed to move over mud have large tyres that spread the vehicle's weight. The pressure under the tyres is relatively low, so the vehicle is less likely to sink into the mud. Caterpillar tracks used on bulldozers and other earth-moving equipment serve a similar purpose. Camels also have large feet so they are less lielly to sink into loose sand.solids-liquids-and-gasses
Explain how pressure works in liquids.Pressure in liquids acts equally in all directions, as long as the liquid is not moving. You can easily demonstrate this using a can with holes punched around the bottom. When the can is filled with water, the water is forced out equally in all directions.solids-liquids-and-gasses
Explain how pressure works in gasses.Gasses also exert pressure on things around them. The pressure exerted by the atmosphere on your body is about 100,000 Pa (although the pressure varues slighly from day to day. However, the pressure inside our bodies is similar, so we do not notice the pressure of the air.solids-liquids-and-gasses
Recall an experiment used to show the effect of pressure.One of the first demonstrations of the effects of air pressure was carried out by Otto van Guericke in 1654, in Magdeburg, Germany. Van Guericke had two large metal bowls made, put them together and then pumped the air out. The bowls could not be pulled apart, even when Guericke attached two teams of horses to the bowls.solids-liquids-and-gasses
Explain Guericke's experiment to show the effects of pressure.You can dot he same experiment as Guericke did using much smaller bowls in the laboratory called Magdeburg hemispheres.&nbsp; When air is inside the spheres, the pressure is the same inside and outside. If the air is sucked out, pressure is only acting from the outside.The hemispheres cannot be pulled aoart until air is let back into them.solids-liquids-and-gasses
Explain how we can work out the equation for pressure difference.The force at the bottom of a column of water is equal to all the weight of water above it. The volume of this water (V) is found by multiplying the area of its base (A) by the height (h) of the column. We can work out the mass (m) of the water by multiplying the volume (A x h) by the density (p).<div><br></div><div>mass of water (m) = (A x h) x p.</div><div><br></div><div>The force (F) on the bottom of the water column is equal to the weight of this volume, which is the mass (A x h x p), multiplied by the gravitational field strength (g), which on earth is 10N/kg.</div><div><br></div><div>F = (A x h x p) x g.</div><div><br></div><div>As we are concerned with the pressure on the base of the column, we divide the force by the area:</div><div><br></div><div>F = A x h x p x g/A.</div><div><br></div><div>The area of the column therefore does not matter, and we can calculate the pressure difference between two points in a liquid using the equation:</div><div><br></div><div>p = h x p x g.</div>solids-liquids-and-gasses
State the equation for pressure difference.p = h x p x g.<div><br></div><div>pressure difference = height x density x gravitational field strength.</div><div><br></div><div>pressure difference (p) = Pa.</div><div>height (m) = m.</div><div>density (p) = kg/m^3.</div><div>gravitational field strength (g) = N/kg.</div>solids-liquids-and-gasses
Explain solids.Solids have a definite rigid shape and they are often very dense. Some solids have high densities because the particles that they are made from are very closely packed in a regular arrangement/lattice. There are strong forces between the particles, which give solid objects their definite shape, and, in some materials, a great deal of strength.<div><br></div><div>Although the particles are held together by strong forces, they can still move. They vibrate about their fixed positions in the solid. When we supply energy to a solid by heating it, the particles vibrate more - they move more quickly. We notice the increase in the kinetic energy of the particles in a substance as an increase in the temperature of the substance.</div>solids-liquids-and-gasses
Define density.The density of a substance is a measure of how tightly packed the particles are.solids-liquids-and-gasses
Explain liquids.Liquids share a property with gases - they have no definite shape. However, the particles that make up liquids tend to stick together unlike gas particles. Liquids will occupy the lowest part of any container but gasses wil expand to fill any container they are in. Liquids have much greater densities than gases. This is because the particles in liquids are still very close together, like they are in solids. Because the particles in liquids are close together, they still attract one another and hold together. In liquids, there is no fixed pattern and the particles can move around more freely than in solids. As we heat liquids, the movement of the particles becomes more energetic.solids-liquids-and-gasses
Explain gasses.In gasses, the particles are very spread out, with large spaces between them. This means that the forces holding them together are small. Gasses have very low densities and no definite shape. Gasses can also be squashed into a a smaller space (compressed). Particles of a gas are moving randomly all the time. The particles will bump into anything in the gas, or into the walls of the container, and the forces caused by these collsions are responsible for the pressure the gasses exert.<div><br></div><div>Solids abd liquids are very difficult to compress because the paerticles in them are almost as close together as they can be.</div>solids-liquids-and-gasses
Do solids, liquids and gasses have a definite shape?Solid = Yes<div>Liquid = No</div><div>Gasses = No</div>solids-liquids-and-gasses
Can solids, liquids and gasses be easily compressed?Solids = No<div>Liquids = No</div><div>Gasses = Yes</div>solids-liquids-and-gasses
Do solids, liquids and gasses have a relative density?Solids = High<div>Liquids = High</div><div>Gasses = Low</div>solids-liquids-and-gasses
Can solids, liquids and gasses flow (are they fluids)?Solids = No<div>Liquids = Yes</div><div>Gasses = Yes</div>solids-liquids-and-gasses
Do solids, liquids and gasses exoand to fill all available spaces (fill their container)?Solids = No<div>Liquids = No</div><div>Gasses = Yes</div>solids-liquids-and-gasses
Explain the particles (molecules) in a solid.The particles (molecules) in a solid:<div><br></div><div>- are tightly packed.</div><div>- are held in a fixed pattern (regular lattice) or crystal structure by strong forces between them.</div><div>- vibrate around their fixed positions in the structure.</div>solids-liquids-and-gasses
Explain the particles (molecules) in a liquid.The particles (molecules) in a liquid:<div><br></div><div>- are tightly packed (still very close together, like in solids).</div><div>- are not held in fixed positions but are still bound together by strong forces between them.</div><div>- move at random with no fixed positions.</div>solids-liquids-and-gasses
Explain the particles (molecules) in a gas.The paerticles (molecules) in a gas:<div><br></div><div>- are very spread out.</div><div>- have no fixed positions and the forces between them are very weak.</div><div>- move with a rapid, random motion.</div>solids-liquids-and-gasses
What are the main states of matter?Solid<div>Liquid</div><div>Gas</div>solids-liquids-and-gasses
Define specific heat capacity.The specific heat capacity (s.h.c) (c) of a substance as the amount of energy required to increase the temperature of 1 kilogram of that substannce by 1 degree celsius.solids-liquids-and-gasses
What is the unit for specific heat capacity?"<img src=""paste-6f639223dc732171ce54d46e1970608dd7c2886f.jpg"">"solids-liquids-and-gasses
State the equation for specific heat capacity."<img src=""paste-dbd85d4d781205c71dc9df9bdbf5d3396dadb848.jpg""><div><br></div><div><img src=""paste-ec8073bd3f2293b80905bb5dc6e20cc7d0c64b86.jpg""><br></div><div><br></div><div>change in thermal energy = Joules (J)</div><div>mass = kg</div><div>specific heat capacity =&nbsp;<span style=""color: rgb(35, 31, 32);"">J/kg°C</span></div><div>change in temperature =&nbsp;<span style=""color: rgb(35, 31, 32);"">°C</span></div><div><span style=""color: rgb(35, 31, 32);""><br></span></div><div><span style=""color: rgb(35, 31, 32);"">change in thermal energy = mass x specific heat capacity x change in temperature.</span></div>"solids-liquids-and-gasses
Express how change in temperature can also be expressed in the specific heat capacity equation.<em>∆θ</em>solids-liquids-and-gasses
How is pressure exerted by a gas?When the molecules of a gas hit the walls of a container, they exert a force. The combined effect of the huge number of collisions results in the pressure that is exerted on the walls of the container.solids-liquids-and-gasses
How do you measure the density of a liquid?Measure the mass of a measuring cylinder and then the mass of the meausring cylinder with the liquid in it. Then meausre the volume of the measuring cylinder by reading off it and calculate the density from there.solids-liquids-and-gasses
What is density?Density is the amount of mass (kg) oer a unit of volume (m^3).solids-liquids-and-gasses
What happens if there is more mass in a volume?The more mass there is in the same volume, the more dense the material is.solids-liquids-and-gasses
What is the unit for density?"<div><span style=""color: rgb(35, 31, 32);"">kg/m</span>³<span style=""color: rgb(35, 31, 32);""><br></span></div><span style=""color: rgb(35, 31, 32);""><div><span style=""color: rgb(35, 31, 32);""><br></span></div><div><span style=""color: rgb(35, 31, 32);"">or</span></div><div><span style=""color: rgb(35, 31, 32);""><br></span></div>g/cm</span>³"solids-liquids-and-gasses
What happens when an object is put in water?When an object is placed in water, it displaces the water. For example, getting in the bath causes the water to rise. The volume of water displaced is equal to the volume of the object put into the water.solids-liquids-and-gasses
State the equation for change in volume of object placed in water.New Volume - Original Volume = Change In Volume Of Object Placed In Water.solids-liquids-and-gasses
What is a eureka can?Larger objects can be put in a eureka can. The water pushed out the spout of the eureka can will show the volume of the large object.solids-liquids-and-gasses
How do you calculate the volume of a sphere?"<img src=""paste-544121969106e3e5232b74b05f72f03676f67214.jpg"">"solids-liquids-and-gasses
How do you calculate the volume of a cylinder?"<img src=""paste-9480950661424c4f400ff0605e729b6f64e9916d.jpg"">"solids-liquids-and-gasses
How do you measure the volume of a cube/cuboid?L (length) x W (width) x H (height).solids-liquids-and-gasses
How do you find the density of an irregularly shaped object?1. Place it on a balance to find its mass.<div>2. Find its volume by placing it in water or a eureka can.</div><div>3. Use the equation for density (p=m/V).</div>solids-liquids-and-gasses
How do you find the density of a liquid?1. Place a measuring cylinder on a balance.<div>2. Pour in the known volume of liquid (read of the meauring cylinder) and measure the mass again on a balance.</div><div>3. Subtract the mass without the known liquid from the mass with the known liquid to find the mass of the known liquid.</div><div>4. Use the equation for density (p=m/V).</div>solids-liquids-and-gasses
How many cm^3's are in 1ml?1solids-liquids-and-gasses
How many m^3's are in 1cm^3?0.000001m^3.solids-liquids-and-gasses
Explain hydraulic systems.Hydraulic systems apply pressure to liquids using pistons. This can make a force multiplier, meaning huge forces can be achieved by applying a little force.<div><br></div><div>Large machines like diggers use hydraulics to lift massive loads. Hydraulics are also used in brakes in cars and notorbikes, and even push bikes.</div><div><br></div><div>Hydraulic systems can transfer forces from one place to another too. For example, a control room and machine for a theme park ride can apply its force to different parts of the ride, if connected by hydraulic pipes.</div><div><br></div><div>It takes many thousand newtons of force to stop a car. This can all be applied with a gentle tap on the brake pedal - thanks to hydraulic multipliers.</div>solids-liquids-and-gasses
Explain how force and area affects pressure.The greater the force, or the smaller the area, the greater the pressure.solids-liquids-and-gasses
What are liquids and what does this mean about the pressure in them?Liquids are incompressuble, which means the pressure is the same at any point in the liquid. If you apply a force on a sealed liquid, you put the liquid under pressure.solids-liquids-and-gasses
List the units for pressure.Pascal (Pa).<div>Newtons per metre sqaured (N/m^2).</div>solids-liquids-and-gasses
What is pressure caused by?Pressure is caused by a force applied over an area.solids-liquids-and-gasses
What happebs if you put liquid in a gas syringe?When you compress a liquid, its particles are pushed closer together. If you put a liquid in a gas syringe and make sure there is no air, when you push down on it you are exerting pressure on the liquid. The liquid then tries to escape by pushing outwards against the walls of its containers. It pushes out in all directions, meaning that the pressure is equal so there are the same amount of newtons of force on every square etre of surface.solids-liquids-and-gasses
Explain why the pressure in a liquid is different at different depths.The pressure in a liquid is different at different depths. Pressure increases as the depth increases. The pressure in a liquid is due to the weight of the column of water above. Since the particles in a liquid are tightly packed, this pressure acts in all directions.For example, the pressure acting on a dam at the bottom of a reservoir is greater than the pressure acting near the top. This is why dam walls are usually a wedge shape. Furthermore, the deeper down you go in the ocean, the greater the pressure of the water, as there is more force (the weight of the water above it) over the same area.solids-liquids-and-gasses
Explain how upthrust occurs in terms of pressure.<div>An object that is partly, or completely submerged, experiences a greater pressure on its bottom surface than on its top surface. This causes a resultant force upwards. This force is called upthrust.</div>solids-liquids-and-gasses
Explain the atmosphere.The atmosphere is tge layer of aur around the earth. The atmosphere is thin compared ti tge size of the earth. The atmosphere becomes less dense as the altitude increases.solids-liquids-and-gasses
Explain atmospheric pressure.Air molecules colliding with a surface causes atmospheric pressure. Atmospheric pressure at sea level is about 101,000 Pa but it is just 27,000 Pa at the cruising altitude of a passenger plane. Atmospheric pressure decreases as the height of a surface above ground level increases. This is because, as the altitude increases, the mumber of air molecules decreases. The weight of air also decreases. In addition to this, there is less air above a surface. This is why aircraft that fly at high altitudes must be pressurised. IIf the aIr pressure is too low, humand cannot take in oxygen quickly enough to meet the bodies needs.solids-liquids-and-gasses
What is temperature?Temperature is a quantity that demonstrates hpw hot something is, and is measured in degrees celsius or kelvin.solids-liquids-and-gasses
"What is change in energy (<img src=""paste-290606d95370f223b318916773998cf43bc78bac.jpg"">) proportional to?""The energy required to heat up something (<img src=""paste-290606d95370f223b318916773998cf43bc78bac.jpg"">) is proportional to the change in tempereature (∆θ). i.e, the hotter you want it, the more energy you must put in.<div><br></div><div>The energy required to heat up (<img src=""paste-290606d95370f223b318916773998cf43bc78bac.jpg"">) is proportional to the mass of the object (m). i.e, the more of a material you have, the more energy you need. A full kettle requires more eenrgy than an empty one.</div>"solids-liquids-and-gasses
What is celsius?Celsius is a measurememtn for temperature. It is a sclar quantity that goes negative. This is the only scalar quantity that goes negative.solids-liquids-and-gasses
What is gas pressure from?Gas pressure is from the total force exerted by particles of gas colliding with the surface of an object.solids-liquids-and-gasses
What happens to the pressure inside an empty paint can when it is heated?As the can is heated, the average speed of the particles increase. This is because, they have more kinetic energy. Because of this increase in spee/energy of the particles, there are more collisions between the particles and the sides of the can, and the force of these collisiond will graudally increase as the particles move faster and with mire kinetic energy from the increase of heat. However, the number of pasrticles in the tin will stay the same. Because of the increase in collisions, the pressure of the tin will increase, eventually gaining more pressure than its outer surroundings, As the particls are colliding with the sides of the tin, the volume of the tin will stay the same but with enough pressure it iwll break.solids-liquids-and-gasses
Explain how pressure increases when gasses are heated.- Particles in a gas are constantly moving in random directions and speeds.<div><br></div><div>- If you increase the tempertaure of the gasm more energy is transferred to the kinetic energy stores of gas particles.</div><div><br></div><div>- Thus means their speed of movement increases.</div><div><br></div><div>- A higher temperature means a higher average energy.</div><div><br></div><div>- Gas particles constantly collide as they move at high speeds.</div><div><br></div><div>- When they collide with a surface, they exert a force on it.</div><div><br></div><div>- Pressure = Force/Area, so when a force is exerted on a surface, this causes a pressure to also be exerted on the surface.</div>solids-liquids-and-gasses
What is the density of water?1g/cm^3solids-liquids-and-gasses
What are changes in state?Physical changes (only the form of a sunstance changes).solids-liquids-and-gasses
Explain how bubbles from when boiling a liquid and how melting occurs.When you heat a liquid, the extra energy is transferred into the particles' kinetic energy stores, making them move faster. Eventually, when enough of the particles have enough energy to overcome their attraction to eachother, big bubbles of gas form in the liquid - this is boiling.<div><br></div><div>This is similar to when you heat a solid. The extra energy makes the particles vibrate faster until eventually the forces between them are partly overcome and the particles start to move around - this is melting.</div>solids-liquids-and-gasses
Explain why density changes when a change of state occurs but why the mass doesn't change.Provided you're working with a closed syste,, the mass of a substance isn't affected when it changes state. This is because, the mass of a substance is the mass of its particles, and the particles aren't changing, they're just being rearranged<div><br></div><div>However, when a substance changes state its volume does change. The particles in most substances are closer together when they're solid than a liquid, and are closer together when they're a liquid than a gas.</div><div><br></div><div>Since density = mass/volume, then density must change too. Generally, substances are most dense when they're solids and least dense when they're gasses, levaing liquids in the middle.</div>solids-liquids-and-gasses
What is kinetic theory?The idea that all matter is made up of very small, constantly moving particles.solids-liquids-and-gasses
Explain what happens to the gas pressure as the tmperature of the gas or volume of gas increases.The speed of gas particles depends on the temperature of the gas. The higher the temperature, the faster the particles move and the more often they collide with the container. The force exerted by each particle during a collision also increases as the temperature increases.<div><br></div><div>So increasing the temperature of a fixed volume of gas increases its pressure.</div><div><br></div><div>Alternatively, if temperature is constant, increasing the volume of a gas means the particles get more spread out and hit the walls of the container less foten.</div><div><br></div><div>So, increasing the volume of a fixed temperature of gas decreases its temperature.</div>solids-liquids-and-gasses
How can a change in pressure cause a change in volume?A gas exerts a force on its container due to collisions between the particles and the walls of the container. These collsiions happen in random directions, but add together to produce a net (overall) force at right angles tot he wall of the container. Unless it's in a vacuum, the outside of a gas container will also be under pressure from whatever is around it. For containers without a fixed volume, the volume of the container is constant when the pressure of the gas inside pushing outwards is equal tot he pressure of the air outside pushing inwards. You can change the volume of a gas in a container that doesn't have a fixed volume by changing either the internal or external pressure on the container.solids-liquids-and-gasses
Explain how you can change the pressure of a gas inside a container by heating or cooling (e.g in a balloon).As the balloon is heated, the gas particles inside it gain energy and move around quicker. This increases the pressure of the gas inside the balloon. The outward pressure of the gas inside the balloon is now larger than the inward pressure caused by the surroundings. The balloon (and so the volume of the gas) expands until the pressures are equal once more. Cooling the gas int he balloon has the opposite effect - the outward pressure is smaller than the inward pressure, so the gas inside the balloon is compressed.solids-liquids-and-gasses
Explain how you can change the external pressure on a gas.In a number of ways:<div><br></div><div>For a gas in an air-tight syringe, pushing hard on the plunger increases the inward pressure on the gas, so that it is larger than the outward pressure. This causes the gas inside of the syringe to be compressed.</div><div><br></div><div>Atmospheric pressure decreases as altitude increases, so as a container of a gas rises, the inward pressure decreases. This causes the gas rto expand as the altitude increases.</div>solids-liquids-and-gasses
What can doing work on a gas do and use the example of a bike pump to prove this?Doing work on a gas can increase its internal energy, which increases its temperature. You can do work on a gas mechanically, e.g with a bike bump (you can also do work on a gas when you heat it up). The gas exerts pressure on the plunger of the pump, and so exerts a force on it. Work has to be done against the force to push down the plunger. This transfers energy to the kinetic energy stores of the gas particles, so increases the internal energy and therefore the temperature. If the pump is connected to a tyre, for example, some of this energy is transferred from the gas to the thermal energy store of the tyre, abd you will feel the tyre getting warmer as you pump it up.solids-liquids-and-gasses
What is fluid pressure and how does it work?Fluid pressure is the pressure caused by the collisions of gas or liquid particles on a given surface. Fluid pressure always exerts a force at right angles to any surface in contact with the fluid. The force on a surface due to fluid pressure depends on the area of the object the fluid is in contact with. The properties of a fluid and the atmospheric pressure surrounding the fluid affect the fluid pressure.solids-liquids-and-gasses
Explain how fluid pressure increases with depth.For a given liquid, the density is uniform (the smae everywhere) and it doesn't vary with shape or size. The density of a gas can vary though. Assuming their particles have the same mass, a denser fluid has more particles in a certain space than a less dense one. This means there are more particles that are able to collide so the pressure is hugher at a given depth in the denser fluid. As the depth of a fluid increases, the number of particles above that point increases. The weight of these particles above that point increases. The weight of these particles adds to the pressure felt at that point, so fluid pressure increases with depth.&nbsp;solids-liquids-and-gasses
Explain how objects in fluids experience upthrust.When an object is submerged in a fluid (either partially or completely), the pressure of the fluid exerts a force on it from every direction. Pressure increases with depth, so the force exerted on the bottom of the object is larger than the force acting on the top of the object. This causes a resultant force upwards, known as upthrust. The upthrust is equal to the weight of fluid that has been displaced by the object (e.g the upthrust on an ild boot is equal to the weight of a boot shaped volume of water).solids-liquids-and-gasses
Explain how an object floating depends on its weight compared to the upthrust force.If the upthrust on an object is equal to the object's weight, then the forces balance and the object floats. If an objects weight is more than the upthrust, the object sinks. This means that whether or not an object will float depends on its density. An object that is less dense than the fluid it is placed in displaces a volume of fluid equal to its weight before it is completely submerged. At this point, the objects weight is equal to the upthrust, so the object floats. An object that is denser than the fluid it is placed in is unable to displace enough fluid equal to its weight. This means that its weight is always larger than the upthrust, so it sinks.solids-liquids-and-gasses
Explain how atmospheric pressure decreases with height.The atmosphere is a layer of air that surrounds Earth. It is thin compared to the size of the Earth. Atmospheric pressure is created on a surface by air molecules colliding with the surface. As the altitude (height above Earth) increases, atmospheric pressure decreases, as shown on certain graphs. These graphs are curved because atmospheric pressure is affected by the density of the atmosphere, which also varies with height. As the altitude increasesm the atmosphere gets less dense, so there are fewer aur molecules that are able to collide with the surface. There are also fewer air molecules above a surface as the height increases. This means that the wiehgt of the air above it, which contributes to atmospheric pressure, decreases with altitude.solids-liquids-and-gasses
Explains what happens when you put in energy to break bonds between praticles.When you heat a solid or liquid, you're transferring energy to the kinetic energy stores of the particles in the substance, making the particles vibrate or move fatser. When a substance is melting or boiling, you're still putting in energy, but the energy's used for breaking bonds between particles, rather than raising the temperature. When a substance is condensing or freezing, bonds are forming between particles, which releases energy. This means the temperature doesn't go down until all the substance has turned into a liquid (condensing) or a solid (freezing). This is the same when heating uo a substance.solids-liquids-and-gasses
State Newton's third law and simplify it.For every action, ther is an equal and opposite reaction.<div><br></div><div><br></div><div><br></div><div>Simply put, when you push simething it pushes you back just as hard, but in the opposite direction.</div>forces-year9
Give an example of Newton's third law.When you sit down, your weight pushes down on the seat. The seat pushes back on you with an equal, but upward, force.<div><br></div><div>or</div><div><br></div><div>When a car is on a road, the weight of the car is pushing down on the ground. Although the weight is shown coming from the centre of gravity of the car, it acts through the wheels pressing down on the ground. The totl reaction force from the ground acting upward on the wheels is the same as the weight of the car. It is this reaction force that stops the car sinking into the ground.</div>forces-year9
What is the difference between action and reaction forces and balanced forces?It can sometimes be difficult to sort out action and reaction forces from balanced forces. Balanced forces act in opposite directions on the same object. Action and reaction forces also act in opposite directions, but are always acting on different objects.forces-year9
Explain how rocket motors work.Rocket motors use the principle of conservation of momentum to propel spacecraft through space. They produce a continuous, controlled explosion that froces large amounts of fast-moving dasses (produced by the fuel burning) out of the back of the rocket. The spacecraft gains an equal amount of momnetum in the opposite direction to that of the moving exhaust gasses.forces-year9
Explain how the law of conservation of momentum principle can be applied to explosions.The conservation of momentum principle can be applied to explosions. An explosion involves a release of energy, causing things to fly apart. The momentum before and after the explosion is unchanged, though there will be a huge increase in movement energy.forces-year9
What is specific latent heat for heating and cooling?The specific latent heat (SLH) of a change of state of a substance is the amount of energy needed to change 1kg of it from one state to another without changing its temperature. For cooling, the specific latent heat is the energy released by a change in state.forces-year9
Explain how speed works in a car.The average speed of the car during the journey is the total sdistance travelled, divided by the time taken for the journey. If you look at the speedometer in a car, you will see that the speed of the car changes from instant to instant as the acccelerator or brake is used. The speedometer therefore shows the instantaneous speed of the car.forces-year9
State the equation for speed."<img src=""paste-58753d6297ab3231f1799682361a1caac70b7623.jpg"">"forces-year9
Explain how the speed of a car is monitored on roads.The police sometimes use a mobile speed camera to check that drivers are keeping to the speed limit. Speed guns use microprocessors to produce an instant reading of the speed of a moving vehicle.forces-year9
Explain how you can conduct an experiment to measure car speed.1. Measure 50m from a start point along the side of the road.<div>2. Start a stopwatch when your partner signals that the car is passing the start point.</div><div>3. Stop the stopwatch when the car passes you at the finish point.</div><div><br></div><div>Using the measurements made with your speed trap, you can work out the speed of teh car, using the v = s/t equation.</div>forces-year9
Where do distance and time go on a distance/time graph?Distance = y axis.<div>Time = x axis.</div>forces-year9
"Explain what is happening in terms of speed in each of these graphs.<img src=""paste-2adae1688c370cd0bbddf5ba5cdaf36a97fce5f8.jpg"">"A = Stationary.<div>B = Constant Speed.</div><div>C = Acceleration.</div>forces-year9
Compare distance and displacement and what is displacement?Distance is simply how far na object has travelled, even if it is going back to the point where it started.<div><br></div><div>Comparatively, displacement means 'distance travelled in a particular direction' from a specified point. So if the object was originally travelling in a northerly direction, the negative gradient of a graph means that it is now travelling south. Sisplacement is an example fo a vector quantity.</div>forces-year9
Compare vector and scalar quantities.Vector quantities have magnitude (size) and a specific direction (e.g displacment, velocity).<div><br></div><div>Scalar quantities only have a magnitude (size) and no specific direction (e.g distance, speed).</div><div><br></div><div>You can therefore have negative vecotr values, but not negative scalar values (apart form celsius).</div>forces-year9
Explain velocity.Velocity is also a vector quantity. Velocity is speed in a particular direction. If a car travels at 50km/h around a bend, its speed is constant but its velocity will be changing for as long as the&nbsp; direction that the car is travelling in is changing.forces-year9
Define acceleration.Acceleration is the rate at which objects change their velocity.forces-year9
State the equation for average velocity.Average Velocity = Increase In Displacement (Distance)/Time Taken.forces-year9
State the equation for acceleration."<img src=""paste-b7c21900ebc46d76b13a77b3e889b1af5251b8d7.jpg""><div><br></div><div><img src=""paste-4b1af561fae261574485fb8ac8596ac933ed7fd2.jpg""><br></div><div><br></div><div><br></div><div><div>a&nbsp;= acceleration (m/s/s or m/s²) (other units can be used, such as cm/s^2)</div><div>v&nbsp;=&nbsp;final velocity (m/s).</div><div>u&nbsp;=&nbsp;initial velocity (m/s).</div><div>t&nbsp;= time (s).</div></div>"forces-year9
What is deceleration and what does this mean?Deceleration means slowing down. This means that a decelerating object will have a smaller final velocity than its starting velocity. If you use the equation for finding the acceleration of an object that is slowing down, the answer will have a negative sign. A negative acceleration simply means deceleration.forces-year9
Explain Galileo's experiments about measuring acceleration.Galileo wanted to discover how the distance travelled by a ball depends on the time it has been rolling. In this version of the experiment, a ball rolling down a slope strikes a series of small bells as it rolls. By adjusting the positions of the bells carefully, it is possible to make the bells ring at equal intervals of time as the ball passes. Galileo noticed that the distances travelled in equal time intervals increased, showing that the ball was travelling faster as time passed. Galileo did not have an accurate way of measuring time, but it was possible to judge equal time intervals accurately simply by listening.&nbsp;forces-year9
What did Galileo also notice with his experiment where he was measuring acceleration?Galileo also noticed that the distance travelled by the ball increased in a predictable way. He showed that the rate of increase of speed was steady or uniform. We call this uniform acceleration. Most acceleration is non-uniform - that is, it changes from instant to instant.forces-year9
What happens in terms of plotting points on a graph if you are plotting average velocity?The points are plotted in the middle of each successive interval as it's an average.forces-year9
Explain how we can set up a modern version of Galileo's experiment.Today, we can use data loggers to make accurate measurements that are collected and analysed by a computer. A spreadhseet program can be used to produce a velocity-time graoh. You can use a glider on a slightly sloping air-track to conduct this experiment. The air-track reduces friction because the glider rides on a cushion of air that is pushed continuously through holes along the air-track. As the glider accelerates down the sloping track, the card stuck on it breaks a light beam, and the time that the glider takes to pass is measured electronically. If the length of the card is measured, and this is entered into the spreadsheet, the velocity of the glider can ve calculated by the spreadsheet program using v=s/t.forces-year9
Explain how we can use the gradient in a velocity-time graph.The slope or gradient of a velocity-time graph is found by dividing the increase in the velocity by the time taken for the increase. Therefore, the gradient of a velocity-time graph is the acceleration of the object.forces-year9
"Label the lines on this displacement-time graph.<img src=""paste-04f2af5a3464f70f697e26fb9853b75f1564f0f2.jpg"">"Yellow = Decelerating to 0 Point.<div>Green = Fast Constant Speed.</div><div>Blue 1 = Decelerating.</div><div>Blue 2 = Accelerating.</div><div>Red 1 = Constant Speed.</div><div>Red 2 = Stationary.</div><div>Red 3 = Returning To 0 Point At Constant Speed.</div>forces-year9
"Explain what is happening in each of these velocity-time graphs.<img src=""paste-98b56baa5046ef388e0461be88eef2c12c2a278d.jpg""><img src=""paste-479ab6c95b5691a4d8277277dbd92a30a14e71a2.jpg"">"1. Constant acceleration.<div>2. Constant deceleration (negative acceleration).</div><div>3. Rate of acceleration increasing.</div><div>4. Rate of deceleration increasing.</div><div>5. Rate of acceleration decreasing.</div><div>6. No acceleration (going at constant speed).</div>forces-year9
How do you work out the average velocity from a velocity-time graph?Average Velocity = Initial Velocity + Final Velocity/2&nbsp;<div><br></div><div>or&nbsp;</div><div><br></div><div>u+v/2.</div>forces-year9
What does the area under a velocity-time graph show?The distance travelled by (displacement of) the object in a particular time interval.forces-year9
State the equation for acceleration using final velocity, initial velocity, and distance and its rearrangements."<img src=""paste-2e2c60a4812ef669edf8b7004e861cd0d8f1410b.jpg""><div><img src=""paste-a31ab1f293f7db37773bc923c238082b8c49d4db.jpg""><br></div><div><img src=""paste-f9c9aa02bd0630343a232d3165a14d0f8d31ad5f.jpg""><br></div><div><img src=""paste-457fbc4a3563245372d7720f1645bcec20dc3ac0.jpg""><br></div><div><br></div><div><ul><li>final velocity (<em>v</em>) is measured in metres per second (m/s)</li><li>initial velocity (<em>u</em>) is measured in metres per second (m/s)</li><li>acceleration (<em>a</em>) is measured in metres per second squared (m/s²)</li><li>displacement (<em>s</em>) is measured in metres (m)</li></ul></div>"forces-year9
Is force a vector or scalar?Force is another example of a vector.forces-year9
Explain the unit for force.The unit used to measure force is the newton (N), named after Sir Isaac Newton. Newton's study of forces is vital to our understanding of them today. A force of one newton will make a mass of one kilogram accelerate at one emtre per second squared.&nbsp;forces-year9
Explain how unbalanced and balanced forces work in terms of a tug of war scenario.In a tug of war contest, the two teams are pulling on the rope in opposite directions. For much of the time, the rope doesn't move because the two forces are balanced. This means that the forces are the same size but act in opposite directions along the line of the rope. There is no unbalanced force in one direction or the other. In this case, if the rope is stationary, it remains stationary. Eventually, one of the teamms will become tired and its pull will be smaller than that of the other team. When the forces acting on the rope are unbalanced, the rope will start to move in the direction of the grater force. There will be an unbalanced force in that direction. The rope was stationary and the unbalanced forces acting on it caused it to accelerate.forces-year9
What happens if a force is balanced or unbalanced?Balanced = when the forces acting on something are balanced, an object does not change the way it is moving.<div><br></div><div>Unbalanced = unbalaced forces acting on an object cause an object to change the way it is moving.</div>forces-year9
Explain how balanced and unbalanced forces work in terms of a car that is designed to have an enormous acceleration from the rest moving.As soon as the car starts to move, the forces that oppose motion - friction and drag - must be overcome. The thrust of the engine, to start with, is much greater than the friction and drag forces. This means that the forces acting on the car in the horizontal direction are unbalanced and the result is a change in the way that the car is moving - it accelerates. Once the friction forces balance the thrust, the car no longer accelerates - it moves at a steady speed.forces-year9
What is friction?Friction is the force that causes moving objects to slow down and finally stop.forces-year9
Explain what happens as work is done by the friction force and give some examples of where it is useful in small and large amounts.The kinetic energy of a moving object is transferred to heat as work is done by the friction force. For an ice skater, the force of friction is very small, so the ice skater is able to glide for long distances without having to do any work. It is also the force that allows a car's wheels to grip the road and make it accelerate - very quickly in the case of racing cars.forces-year9
What can reducing and increasing friction help with?Scientists have worked hard for many years to develop some materials that reduce friction and others that increase friction. Reducing friction means that machines work more efficiently (wasting less energy) and do not wear out so quickly. Increasing friction can help to make tyres that grip the road better and to make more effective brakes.forces-year9
When does friction occur and how can it be reduced?Friction occurs when solid objects rub against other solid objects and also when objects move through fluids (liquids or gases). Sprint cyclists and Olympic swimmers now wear special materials to reduce the effects of fluid friction, so they can achieve faster times in their races. Sometimes, fluid friction is very desirablee. For example, when someone uses a parachute after jumping from a plane.forces-year9
Explain how forces can change the shape of an object.Forces can change the shape of an object. Sometimes, the change of shape is temporary, as in the suspension spring in a mountain bike. Sometimes, the shape of the object is permanently changed, like a crushed can or a car that has collided with another object. A temporary change of shape may provide a useful way of absorbing and storing energy, as in the spring in a clock. A permanent change may mean the failure of a structure like a bridge to support a load.&nbsp;forces-year9
Explain stretching a material.If you apply a force to an elastic band, it shape changes - the band stretches and gets longer. All materials will stretch a little when you put them under tension (pull them) or shorten when you compress or squash them. You can stretch a rubber band quite easily, but a huge force is needed to cause a noticeable extension in a piece of steel of the same length.forces-year9
Compare stretching elastic materials and plastic materials.Some materials, like glass, do not change shape easily and are brittle, breaking rather than stretching noticeably. Elastic materials do not break easily and tend to return to their original shape when the forces acting on them are removed. Other materials, like putty and modelling clay, are not elastic ut plastic, and they change shaoe when even quite small forces are applied to them.forces-year9
What are springs and how do they work?Springs are coiled lengths of certain types of metal, which can be stretched or compressed by applying force to them. They are used in many different situations. Sometimes, they are used to absorb raised bumps int he road as suspension springs in a car or bicycle. In beds and chairs, they are used to make sleeping and sitting more comfortable. They are also used in door locks to hold them closed and make doors close automatically.<div><br></div><div>SPRINGS CHANGE LENGTH WHEN A FORCE ACTS ON THEM AND THEY RETURN TO THEIR ORIGINAL LENGTH WHEN THE FORCE IS REMOVED.</div><div><br></div><div>This is true, provided you do not stretch the spring too much. If springs are stretched beyond a certain point, they do not spring back to their original length.</div>forces-year9
Explain Hooke's Law and how Hooke discovered this.Robert Hooke discovered another improtant property of springs. Hooke measured the increase in length (extension) produced by different load forces on springs. The graph he obtained by flotting force against extension was a straight line passing through the origin. This shows that the extension of the spring is proportional to the force. This relationship is known as Hooke's Law.forces-year9
What happens if you stretch a spring too far, what is the limit of porportionality, and what is the elastic limit?Hooke's Law only applies if you do not stretch a spring too far. If you do stretch a spring too far, the line on the graph starts to curve at a point called the limit of proportionality. This is the point where the spring stops obeying Hooke's law and starts to stretch more for each increase in the load force. If the load is increased more, a point called the elastic limit is reached. Once you have stretched a spring beyond the elastic limit, it will nto return to its original length as you take the wieghts off the spring.forces-year9
Explain how Hooke's Law applies to wires.Hooke's Law also applies to wires. If you stretch a wire, you will find that the extension is proportional to the load up to a certain a load. Then it may behave like a spring behaves when the limit of proportionality and elastic limit are reached. Wires made of different metals will behave in different ways - some will obey Hooke's Law until the wire breaks; other types of metal will stretch elastically and then plastically before breaking.forces-year9
Do elastic bands obey Hooke's Law and what is significant about them."No, elastic bands don't obey Hooke's Law.<div><br></div><div>If you stretch an elastic band with increasing load forces, you get a graph like this:&nbsp;<img src=""paste-ae51a8059a12414f509c0194d1a5ee59188534e9.jpg"">.</div><div><br></div><div>The graph is not a straight line, showing that elastic bands do not obey Hooke's Law. You may also find that the extension produced by a given load force is different when you are increasing the load force to when you decrease the load force.</div>"forces-year9
What can an unbaanced force be referred to as?A resultant force.forces-year9
Explalin when an object will change its velocity and what unbalanced forces do to an object.An object will not change its belocity (accelerate) unless there is an unbalanced force acting on it. For example, a car travelling along a motorway at a constant speed is being pushed along by a force from its engine, butt his force is needed to balance the forces of friction and air resistance acting on the car. At a constant speed, the unbalanced/resultant force on the car is zero.<div><br></div><div>If there are unabalanced forces acting on an object, the object may accelerate or decelerate depending on the direction of the unbalanced force, The accleereation depends on the size of the unbalanced/resultant force and the mass of the object.</div>forces-year9
What is acceleration proportional and inversely proportional to?Force is proportional to acceleration.<div><br></div><div>Acceleration is inversely proportional to mass.</div>forces-year9
What happens if you double the mass of an object for a given unbalanced/resultant force acting on the object?This means that for a given unbalanced force acting on an object, doubling the mass of the object will halve the acceleration.forces-year9
One newton is the force needed to ____?One Newton is the force needed to make a mass of one kilogram accelerate at one metre per second squared.forces-year9
State the equation for force."<img src=""paste-b4991b04b2f93ca050c68ad7a0f37ec8abe7750b.jpg"">"forces-year9
Explain how you would design a car if you were designing a car for high acceleration.If you were designing a car for high acceleration, the equation F=ma tells you that the car should have a low mass and the engine must provide a high accelerating force.&nbsp;forces-year9
Explain deceleration in a collision.When designing a car, you must also consider the force needed to stop the car. When a moving object is stopped, it decelerates.&nbsp; A negative acceleration is a deceleration.<div><br></div><div>If a large deceleration is needed then the force causing the deceleration must be large too. Usually, a car is stopped by using the brakes in a controlled way, so that the deceleration is not excessive (too much). In an accident, the car may collide with another vehicle or obstacle, causing a very rapid deceleration.</div>forces-year9
Define and explain wieght.The weight of an object is the force that acts on it because of gravity.<div><br></div><div>The weight of an object depends on its mass and the strength of gravity. The gravitational field strength (g) is the force that acts on each kilogram of mass.</div>forces-year9
State the equation for weight."<img src=""paste-104ed8762a1a60eb5bb1d14e8f942c81608890df.jpg""><div><br></div><div>Weight (W) = N (newtons)</div><div>Mass (m) = kg (kilograms)</div><div>Gravitational Field Strength (g) = N/kg (newtons per kilogram)</div>"forces-year9
Explain how parachutes work.When a skydiver jumps from a plane, they will accelerate for a time and eventually reach terminal velocity. Typically, this will be between 150 and 200 km/h. When they open their parachute, this will caue a sudden increase in the drag force. At this velocity (around 200 km/h), the drag frce of the parachute is greater than the weight of the skydiver. This means that the unbalanced/resultant force acting on the parachutist acts upwards, and, for a while, they will decelerate. As they slow down, the size of the drag force decreases, and, eventually, a new terminal velocity is reached. Obviously, the new terminal velocity depends on the design of the parachute, but it musy be slow enough to allow the parachutist to land safely.forces-year9
Explain how we can model terminal velocity in a laboratory.Objects have to accelerate to quite high speeds in air to reach terminal velocity. This makes demonstrating the effect in a laboratory difficult. However, objects falling through liquids also experience a drag force that increases with speed. The sizes of drag forces in liquids are much higher than in gases. This means that objects falling through liquids have a much lower terminal velocity than objects falling through air, and can be used to model terminal velocity. You can use a tall measuring cylinder filled with water and drop small-diameter glass balls into it.forces-year9
What is the gravitational field strength on the moon and what does this mean?1.6N/kg.<div><br></div><div>This means that an object taken from the Earth to the Moon will have less weight, even though it has the same mass.</div>forces-year9
Explain air resistance/drag and what is the drag coefficient?An object moving through air experiences a force that opposes its movement. This force is called air resistance or drag. The size of the drag force acting on an object depends on its shape and its speeed. Cars are designed to have a low drag coefficient. The drag coefficient is a measure of how easily an object move through the air. High-speed trains have an efficient streamlined shape so that air flows more smoothly around them. Streamlined, smooth surfaces produce less drag.forces-year9
Why is it improtant to make fast-moving objects streamlined?It is particularly important to make fast-moving objects streamlined, because the drag force increazes with the speed of the object. The fact that drag increases with speed affects the way that dropped objects accleerate. This is because, the faster they move, the greater the drag force opposing their motion becomes.forces-year9
What forces ar felt by objects falling through the air?Objects falling through the air experince two significant forces: the weight force (that is, the pull of gravity on the object) and the opposing drag force.forces-year9
Explain what happens to an object at the point of release.Point of release - the object has just been released and has a starting velocity of 0m/s. This means that there is no drag (drag forces only act on moving objects). The resulting downward-acting force is just the weight force. This force makes the object accelerate towards the earth.forces-year9
Explain what happens to an object while accelerating.While accelerating - the object is now moving. Because it is moving, it has a drag force acting on it. The drag force acts upwards (up) against the movement. This means that the resulting downward force (acting down) on the object is weight minus the drag force. Drag force has made the resulting downward force smaller, so the acceleration is smaller. All the time that the object is accelerating, it is getting faster. The faster the object moves, the bigger the drag force is.forces-year9
Explain what happens to an object at terminal velocity.At terminal velocity - the drag force has increased to the point where it exactly balances the weight force. Since there is now no unbalanced/resultant force on the object, its acceleration is also 0. The object has reached its terminal velocity and although it is still falling, it will not get any faster.forces-year9
Explain how the 'tread ' of a tyre works.The 'tread' of a tyre is the grooved pattern moulded into the rubber surface. It is designed to keep the rubber surface in contact with the road by throwing water away from the tyre surface.forces-year9
Explain how brakes work.Brakes on cars and bicycles work by increasing the friction between the rotating wheels and the body of the vehicle.forces-year9
What does the friction force between the road and the tyres depend on?The friciton force between the tyres and the road depends on the condition of the tyres and the surface of the road. It also depends on the weight of the vehicle.forces-year9
Explain hwo certain factors can alter the friction force between the tures and the road.If the tyres have a good tread, are properly inflated and the road is dry, the friction force between the road and the tyres will be at its maximu Unfortunately, we do not always travel in ideal conditions. If the road is wet or the tyres are in bad condition, the friction force will be smaller.forces-year9
What is skidding, what are its problems, and how has its impact been reduced?If the brakes are applied too hard, the tyres will not grip the roaf surface and the car will skid. Once the car is skidding, the driver no longer has control, and it will take longer to stop. Skidding can be avoided by applying the brakes int he correct way, so that the wheels do not lock. Most modern cars are fitted with ABS (anti-lock braking system) to reduce the chance of a skid occuring. ABS is a computer-controlled system that senses when the car is about to skid and releases the brakes for a very short time.forces-year9
Explain stopping distances.The Highway Code used in the United Kingdom gives stopping distances for cars travellign at various soeeds. The stopping distance is the sum of the thinking distance and the braking distance. The faster the car is travelling, the greater the stopping distance will be.forces-year9
Explain factors that may increase or decrease thinking distance.It will also depend on a number of other factors, including whether the driver is tired or under the influence of alcohol or other drugs that slow reaction times. Poor visibility (e.g fog) may also make it difficult for a driver to identify a danger and so cause him or her to take longer to respond. Clearly, the longer the driver takes to react, the further the car will travel before braking even stats - that is, the longer the thinking distance will be. Equally clear is the fact that the higher the cars speed, the further the car will tavel during the 'thinking time'. If the distance between two cars is not at least the thinking distance, then in the event of an emergency stop by the vehicle in front, a violent acciden tis inevitable.forces-year9
Explain what happens in an emergency in terms of braking.With ABS (anti-lock braking system) braking, in an emergency, you brake as hard as you can. This means that the braking force will be a maximum and we can work out the decelertion using the F = ma.<div><br></div><div>Vehicles with large masses, like lorrues, will have smaller rates of deceleration fro a given braking force. Therefore, they will travel further while braking.</div>forces-year9
What does the maximum rate of deceleration depend on?The maximum rate of deceleration depends on how hard you can brake without skidding - in poor conditions, the braking force will be lower.forces-year9
What can't vehicles do in terms of stopping and what facotrs can affect braking distance?Vehciles cannot stop instantly. If the car tyres or brakes are in poor condition, or if the road surface is wet, icy, or slippery, then the car will travel further before stopping.forces-year9
State the equation for stopping distance.Stopping Distance = Thinking Distance + Braking Distance.forces-year9
What is the extension of a spring directly proportional to?The load or force applied.forces-year9
What is the difference between the limit fo proportionality and the elastic limit?There is a maximum force, above which the graph curves, showing that extension is no longer proportional to force. The re;ationship is now no-linear - the object stretches mire fir each unit increase in force. This point is known as the LIMIT OF PROPORTIONALITY.<div><br></div><div>Just above the limit of porportionality is the ELASTIC LIMIT. Past this point, the object is permanently stretched.</div>forces-year9
How can you calculate the work done by a force on a spring?You can find the work done for a particular force by calculating the area under the linear section of your force-extension graph up to that value of force.forces-year9
What is a force?A force is a push or a pull on an object that is caused by it interacting with something.forces-year9
What does a free body force diagram show?A free body force diagram shows an isolated body and all the forces acting on it. It should include every force acting on the body, but none of the forces it exerts on the rest of the world. The sizes of the arrows show the relative magnitudes of the forces and the directions show the direections of the forces.<div><br></div><div>Diagrams that show forces acting on different objects are not free body force diagrams.</div>forces-year9
Compare contact and non-contact forces.Sometimes, objects need to be touching for a force to act. E.g, the normal contact force that acts between all touchig objects, or friction between a car's tyre and the road. These are contact forces.<div><br></div><div>Other forces can act between objects that aren't touching (non-contact forces). They're usually caused by interacting fields. E.g the gravitational attraction between objects (like the Earth and Sun) is caused by gravitational fields interacting.</div><div><br></div><div>Interacting magneitc fields can cause attraction or repulsion between magnetic objects, and the electrostatic force causing attraction and repulsion between electrical charges is due to interaction between their electric fields. Thes etwo forces are also non-contact forces.</div>forces-year9
What happens whenever two objects interact?Whenever two objects interact, both objects feel an equal but opposite force (Newton's 3rd Law). This pair of forces is called an interaction pair. You can represent an interaction pair with a pair of vectors (arrows).forces-year9
What does the gradient of a distance-time and velocity-time graph give?Distance-time = speed.<div>Velocity-time = acceleration.</div>forces-year9
What does displacement measure?Displacement is a vector quantity. It measures the distance and direction in a straight line from an object's starting point to its finishing poit.<div><br></div><div>Comparatively, distance is just how far an object has moved. It doesn't involve a direction and is therefore a scalar quantity.</div>forces-year9
Compare speed and velocity.Speed is just how fast you're going with no regard to the direction.<div><br></div><div>Velocity is speed in a given direction.</div>forces-year9
What is acceleration?Acceleration is the change in velocity in a certain amount of time.forces-year9
What is constant acceleration sometimes called?Uniform acceleration.forces-year9
How do you find the speed at a certain time in a distance-time graph?If the graph is curved, to find the speed at a certain time, you need to draw a tangent to the curve at that point, and then find the gradient of the tangent.forces-year9
Define thinking and braking distance.The thinking distance is the distance the car travels in the driver's reaction time.<div><br></div><div>The braking distance is the distance taken to stop once the brakes have been applied.</div>forces-year9
What is braking distance affected by?Speed of car.<div>Mass of car.</div><div>Condition of brakes.</div><div>Friction between tyres and road.</div>forces-year9
What is thinking distance affected by?Reaction time.<div>Speed of car.</div>forces-year9
State Newton's First Law.If the resultant force on a stationary object is zero, the object will remina stationary. If the resultant force on a moving object is zero, it'll just carry on moving at the same velocity.&nbsp;forces-year9
What will a non-zero resultant force always cause and what forms can the acceleration take?A non-zero resultant force will always produce accleeration (or deceleration) in the direction of the force. This 'acceleration' can take five different forms: starting, stopping, speeding up, slowing down and changing direction.forces-year9
How do vehicles start skidding?The brakes of a vehicle do work on its wheels.&nbsp; This transfers energy from the vehicle's kinetic energy store to the thermal energy store of the brakes. Very large decelerations may cause the brakes to overheat (so they don't work as well). They could also cause the vehicle to skid.forces-year9
Explain how velocuty is constantly changing in a circular motion.Velocity is the both the speed and direction of an object. If an object is travelling in a circle (at a costant speed), it is constantly changing direction, so it is constantly changing velocity. This means it's accelerating. This means there must be a resultatn force acting on it. This force acts towards the centre of the circle. This force that keeps something moving in a circle is called a centripetal force.forces-year9
What is weight measured with?A Newton Meter.forces-year9
What is inertia?<div>Until acted on by a resultant force, objects at rest stay at rest and objects moving at a constantt velocity will stay moving at that velocity (Newton's First Law). This tendency to keep moving with the same velocity is called intertia.&nbsp; An object's intertial mass measures how difficult it is to change velocity of an object. Inertial mass can be found using Newton's Second Law of F = ma. Rearranging this gives m = F/a, so inertial mass is just the ratio of force over acceleration.<br></div>forces-year9
Recall a practical to investigate the motion of a trolley on a ramp.1. Measure the mass of the trolley, the unit masses and the hanging hook. Measure the length of the piece of card which will interrupt the light gate beams.&nbsp;<div>2. Adjust the height of the ramp until the trolley just starts to move.</div><div>3. Mark a line on the ramp just before the first light gate - this is to make sure the trolley travels the same distance every time. The light gate will record the initial speed of the trolley as it begins to move.</div><div>4. Attach the trolley to the hanging mass by the string. Hold the trolley still at the start line, and let go of it so that it starts to roll down the slope.</div><div>5. Each light gate will record the time when the trolley passes through it and the speed of that trolley at that time. The acceleration of the trolley can then be found using acceleration = change in speed/time, with the following value:</div><div><br></div><div>- the initial speed of the trolley as it passes through the first light gate, which will be roughly 0 m/s.</div><div>- the final speed of the trolly, which equals the speed of the trolley through the second light gate.</div><div>- the time it takes the trolley to travel between the two light gates.</div>forces-year9
What is weight force, what direction does it move in, and is it contact or non-contact?Weight = the result of a mass being pulled downwards by a gravitational field.<div><br></div><div>Direction = downwards, towards the centre of the planet you are on.</div><div><br></div><div>Non-contact.</div>forces-year9
What is driving force/thrust, what direction does it move in, and is it contact or non-contact?Driving force/thrust = a force that moves a mechanical object (e.g car or plane).<div><br></div><div>Direction = forwards, in the direction the object is moving.</div><div><br></div><div>Contact.</div>forces-year9
What is resistive forces/drag, what direction does it move in, and is it contact or non-contact?Resistive forces/drag = the collective name given to all forces which try to slow an object.<div><br></div><div>Direction = backwards against the direction the object is moving.</div><div><br></div><div>Contact.</div>forces-year9
What is air resistance force, what direction does it move in, and is it contact or non-contact?Air resistance = a force from air which slows down moving objects.<div><br></div><div>Direction = backwards, against the direction the object is moving.</div><div><br></div><div>Contact.</div>forces-year9
What is friction force, what direction does it move in, and is it contact or non-contact?Friction = a force from solids rubbing together. Slows an object and produces heat.<div><br></div><div>Direction = backwards, against the firection the object is moving.</div><div><br></div><div>Contact.</div>forces-year9
What is braking force, what direction does it move in, and is it contact or non-contact?Braking force = a force deliberately applied to slow down a mechanical object.<div><br></div><div>Direction = backwards, against the direction the object is moving.</div><div><br></div><div>Contact.</div>forces-year9
What is reaction (normal contact) force, what direction does it move in, and is it contact or non-contact?Reaction force (normal contact forces) = a force pushing away from a surface at 90 degrees, reacting to a force pushing against it.<div><br></div><div>Direction = away from the surface, at 90 degrees.</div><div><br></div><div>Contact.</div>forces-year9
What is upthrust force, what direction does it move in, and is it contact or non-contact?Upthrust = a force from a fluid which helps keep airplanes in the air and boats from sinking.<div><br></div><div>Direction = upwards under a wing, or from water.</div><div><br></div><div>Contact.</div>forces-year9
What is magnetic force, what direction does it move in,&nbsp;and is it contact or non-contact?Magnetic force = a force coming from a magnetic field.<div><br></div><div>Direction = towards or away from a magnet.</div><div><br></div><div>Non-contact.</div>forces-year9
What is electrostatic force, what direction does it move in, and is it contact or non-contact?Electrostatic force = a force between electrically charged objects.<div><br></div><div>Direction = towards or away from an electric charge.</div><div><br></div><div>Non-contact.</div>forces-year9
What is gravitational force, what direction does it move in, and is it contact or non-contact?Gravitational force = an attractive force between any two masses, arising from a gravitational field surrounding all masses. Usually only noticeable arounf large masses like planets or starts.<div><br></div><div>Direction = towards the centre of mass of an object.</div><div><br></div><div>Non-contact.</div>forces-year9
Compare velocity and speed.Velcoity is the change of displacement per second.<div>Speed is the change of distance per second.</div>forces-year9
Why is acceleration a vector quantity?Acceleration is a vecotr quantity because if you are slwoing down, it would be a negative value.forces-year9
Break down m/s^2 and what is it the unit for?m/s^2 is the unit for acceleration. This means how many m/s the velocity changes every second.forces-year9
Compare average speed and instantaneous speed.Average speed = the mean speed travelled by an object over a whole journey.<div><br></div><div>Instantaneous speed = how fast an pbject is travelling at a given moment in time.</div>forces-year9
What does the x axis mean on a velocity-time graph and why?The x axis on a velocity-time graph means that the object is stationary, as the x axis equates to 0 velocity.forces-year9
What does a straight horizontal line mean on a displacement-time graph and on a velocity-time graph?Displacement-time graph = the object is stationary.<div><br></div><div>Velocity-time graph = the object is moving at a constant velocity.</div>forces-year9
What does a straight, upward, diagonal line mean on a displacement-time graph and on a velocity-time graph?Displacement-time graph = the object is moving at a constant speed.<div><br></div><div>Velocity-time graph = the object is accelerating at a constant rate.</div>forces-year9
What does a straight, downward, diagonal line mean on a displacement-time graph and on a velocity-time graph?Displacement-time graph = the object is reversing at a constant speed.<div><br></div><div>Velocity-time graph = the object is decelerating, eventually to a stop.</div>forces-year9
What does a line curbing upwarfs steeper and steeper mean on a displacement-time graph and on a velocity-time graph?Displacement-time graph = the object is accelerating.<div><br></div><div>Velocity-time graph = the rate of acceleration is increasing.</div>forces-year9
What does a a line getting less and less steep and levelling off mean on a displacement-time graph and on a velocity-time graph?Displacement-time graph = the object is decelerating to a stop.<div><br></div><div>Velocity-time graph = the rate of acceleration is decreasing until the object reaches a constant speed.</div>forces-year9
What does the gradient of the line mean on a displacement-time graph and on a velocity-time graph?Displacement-time graph = the speed of the object.<div><br></div><div>Velocity-time graph = the rate of acceleration.</div>forces-year9
What does an object need to keep moving and what does an object need to slow down or speed up?An object does not need any force to keep moving.<div><br></div><div>An object needs a resultant force in order to slow down or speed up.</div>forces-year9
Explain Newton's First Law.A stationary object will remain stationary.<div><br></div><div>A moving object will continue to move in a constant speed in the same direction.</div><div><br></div><div>If there is a resultant force, you will see a change in velocity.</div><div><br></div><div>The acceleration is always in the direction of the resultant force.</div>forces-year9
State Newton's Second Law.The acceleration of an object is proportional to the resultant force on the object, and inversely proportional to the mass of the object.<div><br></div><div>The greater the force, the greater the acceleration.</div><div><br></div><div>The grater the mass, the lower the acceleration.</div>forces-year9
What is the resultant force on an object equal to?The resultant force on an object is equal to the objects mass mulitplied by its acceleration.forces-year9
Explain mass and weight in terms of vector and scalar quantities.Mass = how much of an object there is. Unit = kg. SCALAR.<div><br></div><div>Weight = the force of an object downwards due to gravitational field. Unit = N. VECTOR.</div>forces-year9
Define, thinking distance, braking distance, and stopping distance.Thinking Distance = The distance travelled during a drivers reaction time.<div><br></div><div>Braking Distance = The distance travelled during braking.</div><div><br></div><div>Stopping distance = Thinking distance + braking distance.</div><div><br></div><div>Stopping distance = How far a vehicle will travel between a hazard occuring and the car stopping.</div>forces-year9
Give some features of thinking distances.- The car travels at a constant speed during this time.<div>- The distance will br increased by anything which increases the reaction time fo the driver.</div><div>- An increase in the distance is a bad thing.</div><div>- Thinking distance is not affected by the state of the vehicle.</div>forces-year9
Give some features of braking distances.- The car decelerates at a constant rate under a constant braking force during this time.<div>- This distance will be increased by anything that affects the friction between the car and the road (or the friction in the brakes).</div><div>- It is not affected by the state the driver is in.</div>forces-year9
Is braking distance directly proportional to speed?No.forces-year9
Compare elastic and plastic materials.An elastic material is a material which is able to recover its original shape once forces have been removed.<div><br></div><div>A plastic material is one whose shape will be changed permanently when forces are removed.</div>forces-year9
State Hooke's Law.The force applied to an elastic material is directly proportionla to the extension of the material.forces-year9
Explain elastic and plastic objects in terms fo energy transfer.When objects are stretched, they take in energy. Sometimes, they transfer the energy to change shape permanently (plastic), or sometimes, they store the energy as elastic potential energy and can go back to their original shape (elastic).forces-year9
Give 2 examples of elastic and plastic materials.Elastic:<div><br></div><div>Metal Spring.</div><div>Metal Wire.</div><div><br></div><div><br></div><div>Plastic:</div><div><br></div><div>Putty.</div><div>Modelling Clay.</div>forces-year9
What happens to springs when a force acts on them and then is removed?Springs change length when a force acts on them, and they return to their original length when the force is removed.<div><br></div><div>If springs are stretched to a certain point, they do not spring back to their original length.</div>forces-year9
Recall the method for a practical to see whether or not a plastic banf obeys Hooke's Law.1. Set up a clamp stand. Then, clamp a half metre ruler to the clamp stand.<div>2. After that, set up another clamp stand and clamp an elastic band to that, ensuring that the ruler and the elastic band line up.</div><div>3. Add masses to the bottom of the elastic band. Ensure that each time you add a new mass on, the overall mass goes up in equal incraments. Once the weight is added, measure the extension.</div><div>4. This is done by taking away the original length of the elastic band from the new length of the elastic band.</div><div>5. Repeat these steps for other overall masses.</div><div>6. Record your results in a table and plot them into a graph. If you graph has a straight line going through the origin, then the force you put on the elastic band is directly proportional to the extension of the eastic band.</div><div>7. However, in this case, the graph will not be directly proportional as the elastic band eventually hits the limit of proportionality. Plot a graph of force and extension.</div>forces-year9
What is thinking distance?When a driver suddenly sees an object blocking the way ahead, it take time for him or her to respond to the new situation before taking any action, such as breaking. This time is called reaction time and will depend on the person driving the car.forces-year9
What is the acceleration caused by a gravitational pull?10m/s^2forces-year9
Where does a non-contact force always happen from?The centre of mass.forces-year10
Why do things move?Because of unbalanced forces.forces-year10
Define the centre of mass of an object.The centre of mass of an object is the point at which the weight acts.forces-year10
What happens when you balance a ruler on your finger in terms of forces and mass?When the ruler is balanced, the anticlockwise moment is equal to the clockwise moment, but there are no downward forces acting in this situation other than the weight of the ruler itself. We know that the weight of the ruler is due to the pull or the earths gravity on the mass of the ruler. The mass of the ruler is equally spread throughout its length. It is not, therefore, surprising to find that the ruler balances at its centre point.<div><br></div><div>We say that that the cebtre of gravity of the ruler is at this point. The weight force of the ruler acts through the centre of gravity - it is the point where the whole of the weight of the ruler appears to act. If we support the ruler at this point there is no turning moment in any direction about the point, and it balances. The centre of gravity us sometimes called the centre of mass.</div>forces-year10
Explain what happens with objects not pivoted at the centre of gravity.A simple see-saw is a uniform beam (plank) pivoted in the middle. The centre of gravity of a uniform beam is in the middle, so the see-saw is pivoted through its centre of gravity. When an object is not pivoted through it's centre of gravity, the weight of the object will produce a turning effect (turning clockwise or anticlockwise).forces-year10
What can a turning force also be called?A moment.forces-year10
Define a moment.A moment is the product of the force applied and the perpendicular distance from the line of action of the force to the pivot point.forces-year10
Recall the equation for a moment.Moment of a force (Nm) = Force (N) x Perpendicular Distance From Pivot (m).<div><br></div><div>m = F x d</div><div><br></div><div>d = m/F</div><div><br></div><div>F = m/d</div>forces-year10
Where should a force be to have its biggest effect?90 degrees to the lever.forces-year10
State the principle of moments.For any systrm in equiliobrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments.forces-year10
When will an object be in balance?When the sum of the clockwise moments = the sum of the anticlockwise moments.forces-year10
Explain how a crane works.The load arm of the crane is long so that the crane can reach across a construction site and move loads backwards and forward along the length of the arm. The weight of the long load arm and the load must be counterbalanced by the large con crete blocks at the end of the short arm that projects out behind the crane controller's cabin. The counterbalance weights must be large because they are positioned closer to the pivot point, where the crane tower supports the crosspiece of the crane. Without careful balance, the turning forces on the support tower could cause it to bend and collapse.forces-year10
What is the case in terms of forces if a beam is not moving?The upward and downward forces must be balanced.forces-year10
What happebs uf a boy is one quarter along a beam?The upward force on the support nearest to him is three-quarters of his weight, and the upward force on the end furthest away from him is one quarter of his weight.forces-year10
What will happen if a boy moves to one end of a beam?The upward force will be at that end of the beam. There will be no upward force at the other end of the beam (excluding the upward force caused by the weight of the bar).forces-year10
State the two equilibrium rules.1. The sum of the clockwise moments = the sum of the anticlockwise moments.<div>2. All linear forces are balanced (upwards forces = downwards forces).</div>forces-year10
Summarize the doppler effect.When a source of a wave (sound or light) is moving relative to an observer, we observe a change in wavelength. If a source is moving towards an observer, the wavefronts (each individual wave) become closer and the frequency increases. The wavelength decreases. If this was sound, we would hear a higher pitch because of this.<div><br></div><div>The opposite of this whole paragraph is true for a source moving away from an observer.</div>waves
List some different types fo waves.Sound waves.<div>Light waves.</div><div>Water waves.<br><div>IR (infrared) waves.</div></div><div>Radio waves.</div><div>EM (electromagnetic) waves.</div><div>Gamma waves/</div><div>Microwaves.&nbsp;</div>waves
Define a wave.A wave transfers energy from one place to another without a net movement of the medium (without transferring matter) (without moving the place through which the wave has travelled).waves
Define and give the symbol and unit for wavelength.A wavelength is the length of one complete wave, peak to peak (or trough to trough).<div><br></div><div>Symbol =&nbsp;λ</div><div>Unites = m (metres)</div>waves
Define and give the symbol and unit for amplitude.Amplitude is the maximum disturbance caused by a wave measured from middle to peak or middle to trough.<div><br></div><div>Symbol = A</div><div>Units = m (metres)</div>waves
Define and give the symbol and unit for frequency.Frequency is the number of waves passing a point every second.<div><br></div><div>Symbol = f</div><div>Unit = Hz (hertz) (1/s)</div>waves
Define and give the symbol and unit for period.Period is how long it takes for one wave to pass a point.<div><br></div><div>Symbol = T</div><div>Units = s (seconds)</div>waves
List the equation for frequency.Frequency = 1/Period<div><br></div><div>f = 1/T</div><div><br></div><div>or&nbsp;</div><div><br></div><div>T = 1/f</div><div><br></div><div>or (but this will never come up in an exam)</div><div><br></div><div>1 = f x T</div>waves
Define and give the symbol and unit for wave speed.Wave speed is how fast the wave is travelling.<div><br></div><div>Symbol = v</div><div><br></div><div>Units = m/s</div>waves
Define and give the symbol and unit for wavefront."<span style=""color: rgb(35, 31, 32);"">This is an imaginary surface that we draw to represent the vibrating part of a wave. If you draw semi-circular sound waves spreading out from a speaker, the semi-circular lines are the wavefront.</span>"waves
Define and give an example of a transverse wave.Transverse waves are waves whereby the oscillation of the medium (vibration of the thing being shaken) is perpendicular to the direction of energy transfer.<div><br></div><div>e.g water waves/light waves/EM (electromagnetic) waves.</div>waves
Define and give an example of a longitudinal wave.A longitudinal wave is a wave whereby the oscillation of the medium (vibration of the thing being shaken) is parallel to the direction of energy transfer.&nbsp;<div><br></div><div>e.g sound waves/ultrasound waves/seismic waves.</div>waves
Define the crest and trough.The crest is the top point of a wave and the trough is the bottom point of a wave.waves
What is a wavefront?Wavefronts are creeted by overlapping lots of different waves. A wavefront is a line where all the vibrations are in phase and the same distance from the source.waves
What is a wave?Waves are a way of transferring energy from place to place. As we can see, we often use them to transfer information. All these transfers take place with no matter being transferred.waves
Give an example of waves working in water.Waves are produced if we drop a stone into a pond. The circular wavefronts spread out from the point of impact, carrying energy in all directions, but the water in the pond does not move from the centre to the edges.waves
Summarize transverse waves and give an example of one.Waves can be produced in ropes and springs. If you move one end of a spring from side to side you will see waves travelling through it. The energy carried by these waves moves along the spring from one end to the other, but if you look closely you can see that the coils of the spring are vibrating (shaking) across the direction in which the energy is moving. This is an example of a transverse wave.<div><br></div><div>Transverse waves is one that vibrates, or oscillates, at right angles to the direction inw hich the energy or wave is moving. Examples of transverse waves include light waves and waves travelling on the surface of water.</div>waves
Summarize longitudinal waves and give an example of one.If you push and pull the end of a spring in a direction parallel to its axis, you can again see the energy travelling along it. This time however. the coils of the spring are vibrating in directions that are along its length. This is an example of a longitudinal wave.<div><br></div><div>A longituinal wave is one in which the vibrations, or oscillations, are along the direction in which the energy or wave is moving. Examples of longitudinal waves include sound waves.</div>waves
Explain what happens when a police car is not moving in terms of sound waves.When a police car is not moving, the sound waves we receive from its engine or from its horn arrive as a series of equally (evenly) soaced wavefronts. People in front of and behind the car hear sound of the same frequency and wavelength.waves
Explain what happens when a police car is moving in terms of sound waves.If the car is moving, the wavefronts are no longer evenly spaced. Ahead of the car, the wavefronts will be compressed as the car is moving in this direction. The waves will have a shorter wavelength and a higher frequency. Person B therefore hears a sound that has a higher pitch than when the car was stationary. Behind the car the waves are stretched out so person A hears a sound with a longer wavelength and lowe frequency - that is, the pitch appears to have decreased.<div><br></div><div>These apparent changes in frequency, which occur when a source of waves is moving, is called the Doppler effect, and is a property of all waves.&nbsp;</div>waves
Explain and give an example of refraction of waves.When a pencil is placed in water, the pencil is still straight but it seems to bend at the surface of the water. This happens because light waves in water travel more slowly than light waves in air. This change in speed as they leave the water causes the light waves to change direction. This change in direction is called refraction. All waves - light waves, sound waves, water waves - can be refracted.waves
Explain and give an example fo reflection of waves.All waves can be reflected. If they hit a straight or flat barrier, the angle st which they leve the barrier surface is equal tot he angle at which they meet the surface - that is, the waves are reflected from the barrier at the same angle as thwy strike it. This is described by the 'Law of Reflection' which states that:&nbsp;&nbsp;<div>The angle of incidence is equal to the angle of reflection.</div>waves
Explain the relationship between frequency and wavelength.In a ripple tank, the motor can be adjusted to produce a small number of waves each second. The frequency of the waves is small and the pattern shows that the waves have a long wavelength.<div><br></div><div>At higher frequencues, the water waves have shorter wavelengths. The speed of the waves does not change.</div>waves
Explain a ripple tank.We can study the behaviour of water waves using a ripple tank.<div><br></div><div>When the motor is turned on, the wooden bar vibrates, creating a series of ripples or wavefronts on the surface of the water. A light placed above the tank creates patterns of the water waves on the floor. By observing the patterns, we can see how water waves are behaving.</div>waves
State the equation for wave speed and use it in an example.There is a relationship between the wavelength (λ), the frequency (f) and the wave speed (v) that is true for all waves:<div><br></div><div>wave speed, v (m/s) = frequency, f (Hz) x wavelength&nbsp;λ (m).</div><div><br></div><div>Imagine that you have created water waves with a frequency of 4 Hz. This means that four waves will pass a particular point each second. If the wavelength of the wave is 3m, then the waves travel 12m each second. The speed of the waves is therefore 12m/s.</div>waves
Define wavelength and amplitude.When a wave moves through a substance, its particles will move from their equilibrium (resting position). The maximum movement fo particles from their resting or equilibrium position is called its amplitude (A).<div><br></div><div>The distance between a particular point on a wave and the ame point on the next wave (for example, from crest to crest (or trough to trough (or any other points that match))), is called the wavelength (λ).</div>waves
Define frequency and period.If the source that is creating a wave vibrates quickly, it will produce a large number of waves each second. If it vibrates more slowly, it will produce fewer waves each second. The number of waves produced each second by a source, or the number passing a particular point each second, is called the frequency of the wave (f). Frequency is measured in hertz (Hz). A wave source that produces five complete waves each second has a frequency of 5 Hz.<div><br></div><div>The time it takes for a source to produce one wave is called the time period of the wave (T). It is related to the frequency (f) of a wave by the equation:</div><div><br></div><div>frequency, f (Hz) = 1/time period, T (s)</div><div><br></div><div>f = 1/T</div><div><br></div><div>This equation can also be written as:</div><div><br></div><div>T = 1/f</div>waves
State a method for a practical to investigate how current varies with voltage for different components.1. Set up a circuit with a switch, battery, variable resistor, ammeter, voltmeter and component being investigated (we will use a piece of wire in this experiment).<div><br></div><div>2. Turn the variable resistor to its maximum value.</div><div><br></div><div>3. Close the switch and take the readings from the ammeter and the voltmeter.</div><div><br></div><div>4. Alter the value of the variable resistor again and take a new pair of readings from the meters.</div><div><br></div><div>5. Repeat the whole process at least six times.</div><div><br></div><div>6. Place the results in a table and draw a graph of current (I) againt voltage (V).</div>electricity
How do X-rays work?X-rays pass easily through soft body tissue but cannot pass through bones. As a result, radiographs or x-ray pictures can be taken to check a patient's bones.waves
How are X-rays used in industry?X-rays are also used in industry to check the internal structures of objects - for example, to look for cracks and faults in buildings or machinery - and at airports as part of the security checking procedure.waves
What are the dangers of X-rays and the consequential precuations that have to be taken?Working with X-rays can cause cancer. Radiographers, who take X-rays, are at risk and have to stand behind lead screens or wear protective clothing.waves
What can be used to prevent the damge caused by gamma rays and x-rays (via overexposure)?Lead screens, boxes and aprons.waves
What are gamma rays?Like x-rays, gamma rays are highly penetratung rays and can cause damge to living cells. The damage can cause mutations (negative changes), which can lead to cancer.waves
What are gamma rays used for?Mainly to sterilise medical instruments and to kill microorganisms so that food will keep for longer and to treat cancer using radiotherapy.&nbsp;waves
Explain hwo gamma rays can cause and cure cancer.Gamma rays can both cause and cure cancer. Large doses of gamma rays targeted directly at the cancerous growth can be used to kill the cancer cells completely.waves
What is visible light?Visible light is part of the elctromagnetic spectrum that is visible to the human eye. We use it to see.waves
How does visible light work?Visible light from lasers is used to read compact discs and barcodes. It can also be sent along optical fibres, so it can be used for communication or for looking into hard to reach places such as inside the body of a patient. Visible light can also be detected by the sensors in digital cameras, and used to take still photographs or videos. Information stored on DVD's is also read using visible light.waves
What are the dangers of ultraviolet (UV) light?UV radiation is harmful to human eyes and can damage the skin.&nbsp; &nbsp;UV light causes the skin to tan, but overexposure (too much) will lead to sinburn and blistering. Ultraviolet radiation can also cause skin cancer and blindness. Protective goggles or glasses and skin creams can block the UV rays and will reduce the harmful effects of this radiation.waves
What is ultraviolet (UV) light?Part of the light emitted by the sun is ultraviolet (UV) light.waves
Explain fluorescence under UV light.Some chemicals glow (shine), or fluoresce, when under UV light. This property of UV light is used in security marker pens. The special ink is invisible in normal light but becomes visible in UV light.waves
How does the ozone layer relate to UV raidation and what were the former worries that are now not so prevalent?The ozone layer in the Earth's atmosphere absorbs large quantities of the Sun's UV radiation. In recent years there was real concern that the amount of ozone in the atmosphere was decreasing due to pollution, which would increase numbers of skin cancer. However, there is now evidence to show that the ozone layer is recovering.waves
Why are radio waves significant in terms of wavelength and was are their uses?Radio waves have the longest wavelength in the electromagnetic spectrum. They are use mainly for communication.waves
How do radio waves work?Radio waves are given out (emitted) by a transmitter. As they arrive at an aerial, they are detected and the information they carry can be recerived. Televisions and FM radios use radio waves with the shorter wavelebgths to carry their signals.waves
What are the uses of microwaves?Microwaves are used for communications, radar and cooking foods (N.T don't put the answer 'in microwaves' in the exam - instead say 'in cooking foods'). Radar also uses radio waves to find the position of things.waves
How do microwaves work?Food placed in a microwave oven cooks more quickly than in a normal oven. This is because water molecules in the food absorb the microwaves and become very hot.. The food therefore cooks throughout rather than just from the outside.<div><br></div><div>Microwave ovens have metal screens that reflect microwaves and keep them inside the oven. This is necessary because if the microwaves can cook food, they can also heat human body tissue.&nbsp;</div>waves
Why are mobile phones (which use microwaves) safe for human use?The microwaves used by mobile phones transmit much less energy than those used in a microwave oven, so they do not cook your brain when you use the phone.waves
How are microwaves used in communications?Microwaves are used in communications. The waves oass easily through the Earth's atmosphere and so are used to carry signals to orbiting satellites. From here, the signals are passed on to their destnation or to other orbiting satellites. Messages sent to and from mobile phones are also carried by microwaves. The fact that we are bale to use mobile phones almost anywhere in the home and at work confirms that microwaves can pass through glass, brick and so on.waves
Why is infrared radiation dangerous?Because the human body can be harmed by too much infrared radiation, which can cause skin burns.waves
What is infrared radiation?All objects, including your body, emit infrared (IR) radiation. The hotter an object is, the more energy it will emit as infrared.waves
What are the uses of infrared radiation?Energy is transferred by infrared radiation to bread in a toaster or food under a grill. Electric fires also transfer heat energy by infrared. Infrared radiation is also used in remote controls for televisions, DVD players and stereo systems. It is very convenient for this purpose because the waves are not harmful. They have a low penetrating power and will therefore operate only over small distances, so they are unlikely to interfere with other signals or waves.waves
Why are special cameras designed to detect infrared waves useful?Special cameras designed to detect infrared waves can be used to creaye images even when there is no visible light. These cameras have many uses, including searching for people trapped in collapsed buildings, searching for criminals and checking for heat loss from buildings.waves
What is the electromagnetic spectrum?The electromagnetic spectrum (EM spectrum) is a continuous spectrum of waves, which includes the visible spectrum. At one end of the spectrum the waves have a very long wavelength and low frequency, while at the other end the waves have a very short wavelength and high frequency.waves
What properties do all of the waves on the electromagnetic (EM) spectrum have?- Thery all transfer energy.<div>- They are all transverse waves.</div><div>- They all travel ay 300,000,000 m/s, the speed of light in a vacuum (free space).</div><div>- They can all be reflected and refracted.</div><div>- Wave equations can be applied to all of them.</div>waves
What gives the types of EM wave their different properties?The frequency and wavelength of each type of wave.waves
Order the types of waves in the EM spectrum by frequencies (smallest to largest).SMALLEST<div><br></div><div>Radio waves</div><div>Microwaves</div><div>Infrared (IR)</div><div>Visible light (red)</div><div>Visible light (orange)</div><div>Visible light (yellow)</div><div>Visible light (green)</div><div>Visible light (blue)</div><div>Visible light (indigo)</div><div>Visible light (violet)</div><div>Ultraviolet (UV)</div><div>X-rays</div><div>Gamma rays</div><div><br></div><div>LARGEST</div>waves
Order the types of waves in the EM spectrum by wavelength from largest to smallest.<div>LARGEST</div><div><br></div><div>Radio waves</div><div>Microwaves</div><div>Infrared (IR)</div><div>Visible light (red)</div><div>Visible light (orange)</div><div>Visible light (yellow)</div><div>Visible light (green)</div><div>Visible light (blue)</div><div>Visible light (indigo)</div><div>Visible light (violet)</div><div>Ultraviolet (UV)</div><div>X-rays</div><div>Gamma rays</div><div><br></div><div>SMALLEST</div>waves
How do we hear sounds?Sounds are produced by objects that are vibrating. We hear sounds when these vibrations, travelling as sound waves, reach our ears.waves
What is the speed of sound in air?The speed of sound in air is approximately 340 m/s, although this value does vary a little with temperature.waves
How are the waves of loud and quiet sound different?If a drum is hit hard, lots of energy is transferred to it from the drum stick. The drum skin vibrates up and down with a large amplitude, creating sound waves with a large amplitude and we hear a loud sound. If the drum is hit more gently, less energy is transferred and sound waves with a smaller amplitude are produced. We hear these as quieter sounds.waves
What is the average audible range/hearing range of a human?20Hz - 20,000Hz.waves
How does the audible/hearing range vary and how can you demonstrate the audible/hearing range?The size of the audible range varies slightly from person to person and usually becomes narrower as we get older. You can demonstrate this range by using a signal generator and a loudspeaker to produce sounds at different frequencies.waves
Hpw can higher and lower pitches be heard?Small objects, sich as the strings of the violin, vibrate quickly and produce sound waves with a high frequency. These sounds are heard as notes with a high pitch. Larger objects, such as the strings of a cello, vibrate more slowly and produce waves with a lower frequency. These sounds have a lower pitch.waves
What is frequency?The frequency of a source is the number of complete vibrations it makes each second. We measure frequency in hertz (Hz). If a source has a frequency of 50Hz, this means that it vibrates 50 times each second and therefore produces 50 waves each second.waves
Give an example of how you can hear sound refraction.Although it is not possible to see sound waves being refracted, we can sometimes hear their effect. Standing at the edge of a large pond or lake we can sometimes hear sounds from things on the other side of the water much more clearly than we would expect. This is due to refraction.waves
How can sound waves be refracted?All waves can be refracted, even sound waves. For example, if some parts of a sound wave are travelling through warm air, they will travel nore quickly than those parts travelling through cooler air. As a result, the direction of the sound wave will change. It will be refracted.waves
How does sound wave refraction work?"<img src=""paste-dc75a79c0d1270b60faefea663759e8692e22df6.png""><div><br></div><div>- Most of the sound we hear travels to us in a straight line.</div><div>- But some sound travels upwards.</div><div>- If the temperature conditions are right, then as the sound waves travel through the air they are refracted and follow a curved path downwards.</div><div>- We now receive two sets of osund waves.</div><div>- So the sound we hear seems louder and clearer.</div>"waves
What happens when a sound wave strikes a surface?Sound waves behave in the same way as any other wave. When a sound wave strikes a surface it may be reflected. Like light waves, sound waves are reflected from a surface so that the angle of incidence is equal to the angle of reflection.waves
How do ships discover the depth of the water beneath them?Ships often use echoes to discover the depth of the wayer beneath them. This is called echo sounding. The system of using echoes in this way is called sonar (sound, navigation and ranging).waves
How does echo sounding work?- Sound waves are emitted from the ship and travel to the seabet (sea floor0.<div>- Some of these waves are reflected form the seabed back up to the ship.</div><div>- Equipment on the ship detetcts these sound waves.</div><div>- The time it takes the waves to make this journey is measured.</div><div>- Knowing this time, the depth of the sea below the ship can be calculated.</div>waves
Recall the visible light spectrum.RED<div>ORANGE</div><div>YELLOW</div><div>GREEN</div><div>BLUE</div><div>INDIGO</div><div>VIOLET</div>waves
Recall the electromagnetic (EM) spectrum.RADIO<div>MICRO</div><div>IR</div><div>VISIBLE</div><div>UV</div><div>X-RAY</div><div>GAMMA</div>waves
Give a use fo each of the waves on the EM spectrum.Radio = To carry the signals of televisions.<div>Micro = Microwave oven (for cooking food).</div><div>IR = Thermal imaging cameras.</div><div>Visible = Photography cameras.</div><div>UV = Detecting forged bank notes.</div><div>X-ray = Scanning for broken bones.</div><div>Gamma = Treating cancer via radiotherapy.</div>waves
What is the rule for reflection?For a planer (flat) surface, the angle of incidence is equal to the angle of reflection.waves
Define refraction.By definition, refraction is the change of velocity of a wave (light) as it enters a medium (material) of differing optical density.waves
Can waves refract on a reflective surface and vice versa?Nothing can refract on a reflective surface but some light can reflect during refraction.waves
What does it mean if you have cataracts and how can it be treated?Cataracts means that light cannot enter the eye correctly. The front of the eye becomes so cloudy that one is unable to see. Nowadays, it is possible to remove this damaged part of the eye and replace it with a clear plastic that will allow light to enter the eye again.waves
What are some sources of light and what are luminous objects?There are many sources of light, including the Sun, the stars, fires, light bulbs and so on. Objects such as these that emit their own light are called luminous objects.waves
What happens when emitted light enters our eyes and what are non-luminous?When the emittes light eneters our eyes we see the object. Most objects, however, are non-luminous. They do not emit light. We see these non-luminous objects because of the light they reflect.waves
What are mirrors often used to do and give an example fo this?Change the direction of a ray of light. One example of this is the simple periscope, which uses two mirrors to change the direction of rays of light.waves
What happens as a light ray enters and exits a glass block?As a ray enters a glass block, it slows down and is refracted towards the normal. As trhe ray leaves the glass block it speeds up and is refracted away from the normal. If the ray strikes thr boundary between the two media at 90 degrees, the ray continues without a change fo direction.waves
How do we describe how different materials bend light by different amounts and give values of this for some materials and what does this tell us?Different materials can bend rays of light by different amounts. We describe this by using a number called the refractive index (n). The refractive index of glass is about 1.5 and water is 1.3. This tells us that under similar circumstances, glass will refract light more than water.waves
What equation can you use to calculate the refractive index of a material?We can use the equation below to calculate the refractive index of a material:<div><br></div><div>n = sin i/sin r</div><div><br></div><div>where i is the angle of incidence and r is the angle of refraction.</div>waves