Name: Memorandum
Date:
Subject: Physics stage 9
Total: 105
School: Silveroaks Montessori School
Time: 1h 30min
Sections
Marks
Forces
Electricity
Energy
45
35
25
Total
105
1
Section 1: Forces
1. Complete the formula for area:
[2]
2. Complete the following sentences by filling in the missing words:
[3]
a. When you increase the area the pressure will reduce
b. When you reduce the area the pressure will increase
c. Pressure is measured in N/m² or Pascal (Pa).
3. Use the formula above to answer the below word problems. Be sure to show all work
and write all units.
[16]
a. Calculate the pressure on a man’s foot when a woman who weighs 520 N steps
on his foot with her heel which has an area of 0.001 m² with all of her weight.
520/0.001= 520 000 Pa
b. Calculate the pressure exerted on the floor when an elephant who weighs 2400
N stands on one foot which has an area of 0.4 m².
2400/0.4= 600 Pa
c. Calculate the pressure exerted on the heel of a boy’s foot if the boy weighs 320
N and he lands on one heel which has an area of 0.16 m².
2
320/0.16=2000 Pa
d. How much must a woman weigh (force) if the pressure she exerts while standing
on one foot has an area of 0.6 m², exerts a pressure of 160 Pa?
0,6*160=96N
e. What is the area of a car that touches the road if the car’s weight on that tire is
3072 N and the pressure exerted on the road is 48 Pa?
3072/48=64m²
f. Calculate the pressure exerted on an elevator floor which has an area of 6 m², if
20 people whose combined force is 1500 N are standing on it.
1500/6=250 Pa
g. How much pressure is exerted on a science lab floor if the lab desk has an area
of 1.08 m² and a force of 12 000 N
12000/1.08=111.111
h. How much pressure will be exerted on a diver’s body which has an area of 10
m², if the water column above him weighs 120 000 N?
120000/10=12 000
4. Explain why there is pressure in liquids.
[2]
There is pressure in a liquid because of forces between particles in the liquid acting over
an area.
5. Why does the pressure increase as you go deeper into water?
[1]
The pressure increases because of the weight of the water above you.
6. Why do we use liquids in hydraulic machines?
[1]
Because they are in compressible
7. What are hydraulic machines used for?
[1]
To increase pressure/ pressure multiplier, it is used in brakes, for crushing and making
cars
8. Explain what is meant by gas pressure.
[2]
Gas pressure is caused by particles colliding with the walls of the container.
9. How can you increase gas pressure?
[1]
By decreasing the volume
By increasing the temperature
10. Use the formula below to answer the questions:
[10]
3
a. A loaf of bread has a mass of 500 g and volume of 2500 cm³. What is the density
of the bread?
Density = mass/volumeDensity = 500g / 2500cm3Density = 0.2 g/cm³
b. A block of wood has a mass of 6.0 g and a volume of 12.0 cm³. What is the
density of the block of wood?
Density = mass/volumeDensity = 6.0g / 12.0cm³ Density = 0.5 g/cm³
c. The density of a substance is 4.0 g/cm³. If a sample of the substance has a
volume of 25 cm³, then what is its mass? (Hint:Use the equation: mass = density
× volume.)
Mass = density × volumeMass= 4.0 g/cm³ × 25 cm³ Mass = 100 g
d. You have a lead ball with a mass of 420 g. The density of lead is 10.5 g/cm³.
What is the volume of the ball? (Hint:Use the equation: volume = mass/density.)
Volume = mass/densityVolume = 420 g / 10.5 g/cm³ Volume = 40 cm³
e. A student has a rectangular block. It is 2 cm wide, 3 cm tall, and 25cm long. It
has a mass of 600 g. First, calculate the volume of the block:
Volume = length × width × heightVolume = 25 cm × 2 cm × 3 cmVolume =
150cm3
Then, use that answer to determine the density of the block:
Density = mass/volumeDensity = 600 g / 150 cm³ Density = 4 g/cm³
11. Why are solids and liquids considered more dense than gases?
[1]
Because their particles are packed close together.
12. What does the density of a material depend on?
[2]
The mass and arrangement of the particles.
13. Write down the principle of moments.
[2]
A lever is in equilibrium if the anticlockwise moments balance the clockwise moments.
14. Explain what is meant by the centre of gravity of an object.
[1]
It is the point through which the mass of the object seems to act.
Section 2: Electricity
4
1. Name the two types of charges.
[2]
Positive charge and negative charge
2. What does it mean when an object is neutral?
[2]
When the object has equal numbers of positive and negative charges.
3. Explain the following terms:
[2]
a. Conductor - electrons can move through it.
b. Insulator - the electrons do not move around.
4. How can we reduce the risk of damage caused by lightning to buildings?
[1]
By attaching lightning conductors to buildings
5. Explain how a touch screen works.
[2]
They use a stored electric charge. A sensing circuit connected to the touch screen can
work out where your finger is.
6. Draw a diagram of the electric fields of:
[6]
a. A positive charge
b. A negative charge
c. A positive and negative charge together
7. Complete the following table
[8]
Component
Symbol
Cell
Battery of cells
Wire
Open switch
Closed switch
Buzzer
5
Motor
Lamp
8. Draw the following circuits
[12]
a. A series circuit containing a 3 cell battery and 3 lamps connected in series. Place
a switch in the circuit at a location where it would turn on or off the current
through all lamps.
b. A parallel circuit consisting of a 2 cell battery and 3 buzzers in parallel. Include a
switch that would turn on or off the current through all buzzers.
c. A circuit with a 2 cell battery and a lamp in series connected to two more lamps
in parallel. Include an ammeter placed to measure the current through the
battery.Add a voltmeter to the circuit measuring the voltage of one of the lamps.
d. A parallel circuit with 3 bulbs in parallel and a switch that will turn on or off the
current through one of the bulbs only.
6
Section 3: Energy
1. Complete these sentences by filling in the missing words.
[3]
When you heat up a liquid the particles in it move faster. The same thing happens when
you heat up a gas. When you heat up a solid the particles just vibrate.
2. Explain the difference between temperature and thermal energy.
[2]
Temperature is a measure of how hot or cold something is. Thermal energy is heat.
3. Describe the difference between a conductor and an insulator.
[2]
A conductor transfers thermal energy very quickly. An insulator transfers thermal energy
slowly.
4. How is a convection current formed?
[3]
When a gas or a liquid gets hot it expands and becomes less dense. The less dense gas
or liquid rises and is replaced by cooler gas/liquid. This sets up a convection current.
5. In what form does the energy of the Sun reach us?
[2]
infrared/thermal radiation
6. When will an object emit light?
[1]
Only when it is hot enough.
7. Explain evaporation in terms of how particles behave.
[2]
Liquids evaporate when energy increases the movement of the molecules/particles and
the fast-moving molecules escape.
8. Give two examples for each of the following:
[4]
a. Primary energy sources: coal, oil, gas, uranium
b. Secondary energy sources: electricity, petrol, hydrogen, gasoline
c. Non-renewable resources: coal, oil, gas
d. Renewable resources: solar, wind, water (hydro) and biomass (plants)
9. Explain how a fossil fuel power station works.
[3]
The fossil fuels are burned to turn water into steam. Steam turns the turbine, which turns
a generator to generate electricity.
10. What are the disadvantages of using fossil fuels?
[2]
Burning fossil fuels produce carbon dioxide. Fossil fuels are non-renewable.
11. Name one disadvantage of using renewable energy.
[1]
7
It can be costly
8