7th Grade Energy Unit
What is Work?
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Requirements for work to occur:
1.
Object that the force is being applied to has to move
2.
Force is in the same direction as the object moving.
Energy, Work, and Power
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Work and Energy
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When one thing does work on another some of its energy is transferred to that object.
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The object which the work is done upon gains energy.
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What is the origin of all energy?
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Energy
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Two basic kinds of energy are:
1.
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2.
Potential energy
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Kinetic Energy
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Because the moving object does work, it has energy.
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The energy that an object has due to its motion is called kinetic energy
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Factors Affecting Kinetic Energy
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There are two main factors that affect the amount of kinetic energy that an object has:
1.
Mass
2.
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Factor
How the Kinetic Energy is Affected
Increase in Mass
Increases the amount of Kinetic Energy
Decrease in Mass
Decreases the amount of Kinetic Energy
Increase in Velocity
Increases the amount of Kinetic Energy
Decrease in Velocity
Decreases the amount of Kinetic Energy
A Good Hint
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If you do not know the mass and velocity of an object and want to know if it has a lot of a little kinetic
velocity, ask yourself the following question:
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Calculating Kinetic Energy
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The formula above means that Mass and Velocity do not have the same effect on the kinetic energy of an
object.
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The velocity will have a greater impact than the mass of the object.
Potential Energy
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Stored energy that results from the position or shape of an object is called potential energy.
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This type of energy has the potential to do work.
Types of Potential Energy
Potential Energy is stored Energy
1.
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2.
Elastic Potential Energy
3.
Chemical Energy
4.
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Gravitational Potential Energy
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Potential Energy that is related to an object’s height is called gravitational potential energy.
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Gravitational potential energy = do the work needed to lift it
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Examples of Gravitational Potential Energy:
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Rollercoaster at the top of the hill
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Rock on the edge of a cliff
Elastic Potential Energy
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The potential energy associated with objects that can be stretched or compressed is called elastic potential
energy
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Also known as stored mechanical energy.
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Examples of Elastic Potential Energy:
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Springs
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Chemical Energy
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Chemical compounds are made up of atoms and molecules
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Bonds hold atoms and molecules together.
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Chemical Energy is potential energy stored in chemical bonds that hold chemical compounds together.
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Examples of chemical Energy
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Food
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Batteries
Nuclear Energy
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Nuclear Energy is released during a nuclear reaction.
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Examples of Nuclear Energy:
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The sun
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Nuclear Power plants
Types of Kinetic Energy
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Kinetic Energy is the energy of motion.
1.
Electrical Energy
2.
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3.
Thermal Energy
4.
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Electrical Energy
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The energy of electric charges is electrical energy
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Examples of Electrical Energy:
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Electric current
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Appliances that run on electricity
Electromagnetic Energy
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The electromagnetic spectrum is the range of all possible Electromagnetic radiation.
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Electromagnetic Energy is also called radiant energy.
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Examples:
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Light
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X-rays
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Infrared rays
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Gamma rays
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Thermal Energy
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The faster they more the more kinetic energy an object has.
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The total potential and kinetic energy of the particles of an object are called thermal energy.
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Examples:
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______________ – Lava moving down the side of the hill may be moving slowly but its particles
that make up the lava are moving quickly. Because the particles have a large amount of kinetic
energy the lava has a large amount of thermal energy.
Mechanical Energy
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The form of energy that is a associated with the position and motion of an object is called mechanical
energy.
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An objects mechanical energy is a combination of its potential energy and kinetic energy.
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Thermal Energy and Heat
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Thermal Energy
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Thermal energy depends on:
1.
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2.
The arrangement of the object’s particles.
Heat
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Thermal energy that is transferred from matter at a higher temperature to a lower temperature is called
heat
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Heat is thermal energy moving from a warmer object to a cooler object.
Energy Transformation
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Most forms of energy can be transformed into other forms.
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Types of energy transformation:
1.
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2.
Multiple transformations
Single Transformations
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Remember: work is force exerted on an object causing it to move
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Examples:
1.
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2.
Your body converts the chemical energy in food into thermal energy that your body uses to
maintain its temperature.
Multiple Transformations
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Examples:
1.
The energy needed to strike a match is transformed first to thermal energy. The thermal energy
causes particles in the match to release the stored chemical energy, which is transferred into
thermal energy and the electromagnetic energy you see as light
Energy Chains
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Energy is transformed from one type to another to another and so on.
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When we follow these transformations we get an energy chain.
Transformation Between Potential and Kinetic Energy
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Energy Transformation in Juggling:
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As the ball rises it slows down-kinetic energy decreases. Since the ball is going higher in the air,
the potential energy increases.
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As the ball falls there is a loss in altitude, so the potential energy decreases, at the same time the
ball is moving faster and faster, so the kinetic energy increases.
Conservation of Energy
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According to the law of conservation of energy, energy cannot be created nor can it be destroyed.
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This means:
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If you add up all the new forms of energy = the old forms of energy
Energy and Friction
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Whenever a moving object experiences friction, some the kinetic energy is transformed into thermal
energy.
Formation of Fossil Fuels
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The plants of vast forests that at one time covered Earth provide the energy stored in fuels.
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Examples:
1.
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2.
Lumber
Formation of Fossil Fuels
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These fuels, which include coal, petroleum, and natural gas are known as fossil fuels.
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Fossil Fuels are made of hydrocarbons
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The combustion of fossil fuels provides more energy per kilogram than does the combustion of other fuels.
Relative Amounts of Energy
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twice the energy of wood
Oil and natural gas
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three times the energy of wood
Coal
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Coal is the most plentiful fossil fuel in the United States.
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Advantages
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Easy to transport
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Disadvantages
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Causes erosion
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Runoff causing water pollution
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Oil
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Oil forms from the remains of small animals, algae, and other organisms that lived in oceans and shallow
inland seas hundreds of million years ago.
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What uses petroleum:
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Homes
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Boats
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Trains
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Advantages:
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Oil is one of the most abundant energy resources
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Liquid form of oil makes it easy to transport and use
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Relatively inexpensive
Disadvantages:
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Oil burning leads to carbon emissions
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Where is Oil Located?
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Most oil deposits are located underground in tiny holes in sandstone or limestone.
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Located deep below the surface
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Use sound waves to find oil
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Natural Gas
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Natural Gas is a mixture of methane and other gases.
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Can be compressed and made into a liquid to put in tanks for fuel.
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Advantages:
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Large amount of energy
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Easy to transport
Disadvantages
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Fuel Supply and Demand
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Oil is essential to modern day life
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Since fossil fuels take hundreds of millions of years to form they are considered nonrenewable resources.
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The oil we have today took about __________________________________________________________
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Eventually all the oil on earth will be used up.
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Many nations consume huge amounts of fossil fuels and have a very small reserve.
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United States:
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Uses 1/3 of all oil used in the world
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