Topic 2 - Energy Sources, Uses & Transfers

Question 1

A cyclist has a mass of 64 kg.
The cyclist rides from a flat road to the top of a hill.
The top of the hill is 24 m above the flat road.
Calculate the gain in GPE of the cyclist. (2)
Use g = 10 N/kg
Use the equation
Change in GPE = m × g x change in h

Answer 1

= 64 x 10 x 24 (1)
= 15360 (1)

Question 2

The cyclist returns to the flat road.
The mass of a cyclist is 64 kg.
Calculate the kinetic energy of the cyclist when the cyclist is travelling at 6.0 m/s. (3)
Use the equation
KE = ½ x m x v^2

Answer 2

KE = ½ x 64 x 6^2 (1)
6^2 = 36 (1)
KE = 1152 (1)

Question 3

A cyclist then uses the brakes on the bicycle to stop. Explain what happens to the KE of the cyclist (2)

Answer 3

The KE store decreases to zero (1)
The energy has dissipated (1)
To the surroundings (1)
TE store increases (1)

Question 4

A model train has a mass of 8.0 kg.
It travels at a speed of 1.5 m/s.
Calculate the kinetic energy of the model train.
Use the equation
kinetic energy = ½ × mass × (speed)^2

Answer 4

½ x 8 x 1.5^2 (1)
1.5^2 = 2.25 (1)
9 joules (1)

Question 5

Which of these would be a typical speed for a racing cyclist travelling down a steep straight slope? (1)

A 0.2 m/s
B 2 m/s
C 20 m/s
D 200 m/s

Answer 5

20 m/s

Question 6

A cyclist travels down a slope.
The top of the slope is 20 m vertically above the bottom of the slope.
The cyclist has a mass of 75 kg.
Calculate the change in GPE of the cyclist between the top and the bottom of the slope. (3)
The gravitational field strength, g, is 10 N/kg.

Answer 6

Change in GPE = m x g x change in h (1)
= 75 x 10 x 20 (1)
= 15,000

Question 7

A skier is going down a hill.
She descends through a vertical height of 200 m.
The skier’s mass is 65 kg.
Calculate the change in GPE (2)
Use the equation
Take the gravitational field strength, g, as 10 N / kg.

Answer 7

65 x 20 x 10 (1)
130,000 (1)

Question 8

Electricity can be generated using a water turbine.
Water gains kinetic energy by falling from the top of a dam.
Calculate the minimum height that 7.0 kg of water must fall to gain 1300 J of kinetic energy. (3)

Answer 8

GPE = g x m x h (1)
1300/7 x 10 (1)
18.57 (1)

Question 9

As water enters the turbine at the bottom of the dam, the kinetic energy of 8.0 kg of moving water is 1100 J.
Calculate the speed of the moving water as it enters the turbine. (3)

Answer 9

KE = ½ x m x v^2 (1)
V^2 = 2 x 1100/8 (1)
V = 17 (1)

Question 10

Figure 5 shows a way of projecting a small trolley up a sloping track.
When the button is pressed, a spring is released, which projects the trolley up the track.
The trolley travels up the track, stops and then rolls back down.
The spring always exerts the same force when projecting the trolley.
A student investigates how the mass of the trolley affects the maximum vertical height, h, reached by the trolley.
State the measurements the student should make to complete the investigation.

Answer 10

Measure mass of trolley (1)
Measure vertical height (1)
Repeat for a range of masses (1)
Measure height with a ruler (1)
Weigh the trolley (1)

Question 11

A student lifts a toy car from a bench and places the toy car at the top of a slope.
The student needs to develop the experiment to determine the loss in PE and the gain in KE as the toy car is rolling down the slope.
State the other measurements the student must make. (2)

Answer 11

Vertical height of the slope (1)
The mass of the car (1)

Question 12

Explain how unwanted energy transfers could be reduced in the gear box of a wind turbine (2)

Answer 12

Use of lubrication/oil (1)
To reduce friction (between parts) (1)

Question 13

A student lifts a toy car from a bench and places the toy car at the top of a slope.
Describe an energy transfer that occurs when the student lifts the toy car from the bench and places the toy car at the top of the slope. (2)

Answer 13

Chemical energy (1)
is converted to GPE in lifting (1)

Question 14

State how energy is stored in a spinning flywheel (1)

State one way to increase the amount of energy stored in the flywheel (1)

Answer 14

Kinetically (1)
Increase speed of spinning/mass of wheel (1)

Question 15

Before a car brakes it has kinetic energy.
The kinetic energy decreases as it brakes.
State what happens to the kinetic energy during braking. (1)

Answer 15

Causes heating of the surroundings (1)
Transferred to TE of surroundings (1)
Increases the KE of molecules in the break pads (1)

Question 16

A different cyclist uses a motorised bicycle.
The motorised bicycle is powered by an electric motor.
Calculate how much energy is wasted. (1)

Answer 16

24,000 - 19000 = 5000

Question 17

State what happens to wasted energy. (1)

Answer 17

Dissipitated to the surroundings (1)
Transferred to another form of energy (1)
Reference to thermal energy (1)

Question 18

Coal is a fossil fuel that is burnt in some steam engines.
State two ways that the use of coal might be harmful to the environment. (2)

Answer 18

Releases carbon dioxide/greenhouse gases (1)
Produces carbon monoxide (1)
Produces air pollution (1)
Produces sulphur dioxide (1)
Produces soot/smoke (1)
Mining coal (1)

Question 19

A kettle is used to heat water.
The kettle has an efficiency of 91% in supplying energy to the water.
The thermal energy of the water increases by 3.3 × 10^5 J in 200 s.
Calculate the total amount of energy supplied to the kettle in the 200 s. (2)
Use the equation efficiency = useful energy/total energy

Answer 19

3.3 x 10^5/0.91 (1)
3.6 x 10^5 (1)

Question 20

State two other renewable sources of energy, other than wind (2)

Answer 20

Falling water/hydro (1)
Tides (1)
Sun/solar (1)
Geothermal (1)
Biomass (1)

Question 21

Suggest a reason why it is impossible for a wind turbine to use all the kinetic energy of the
wind. (1)

Answer 21

Air has to be moving on other sides of the blades (1)
Not all of the air hits the blade (1)
Friction within the turbine/generator (1)
Some energy transferred to thermal (1)
It’s fitted with a speed limiter (1)

Question 22

State two non-renewable energy sources (2)

Answer 22

Coal (1)
Gas (natural) (1)
Nuclear/uranium (1)
Oil (1)

Question 23

Solar panels convert energy from the Sun into a form useful in the ISS.
The energy reaching the ISS from the Sun is carried by waves which are: (1)

A transverse and electromagnetic
B electromagnetic but not transverse
C transverse but not electromagnetic
D neither transverse nor electromagnetic

Answer 23

transverse and electromagnetic

Question 24

In one second, the useful energy available from one wing is 34.3 kJ.
The energy incident on the wing from the Sun is 5 times this amount.
What’s the % efficiency of the wing? (3)

Answer 24

5 x 34.3 = 171.5 (1)
34.3/171.5 x100 (1)
20% (1)

Question 25

A wing is in direct sunlight.
The ISS is not receiving energy from the wing. The temperature of the wing remains constant.
Explain why the temperature of the wing remains constant in these conditions. (2)

Answer 25

Rate of energy absorbed from the sun (1)
Is equal to the rate of energy emitted (1)

Question 26

Below is shown a solar cell that produces electricity when receiving energy from the Sun.
When energy from the Sun is absorbed in a silicon layer, it makes charges move. This movement of charges produces a current.

external connection
plastic cover
silicon layer 1
silicon layer 2
back plate

Suggest two reasons why the efficiency of this solar cell at producing electricity from sunlight is less than 100%. (2;

Answer 26

Reflection from external connection/plastic cover (1)
Absorption from external connection/plastic cover/back plate (1)
Transmission through back plate (1)

Question 27

A windfarm generates electrical power from the wind.
State one disadvantage of using the wind to generate electrical power. (1)

Answer 27

Unreliability (1)
Pollution (1)

Question 28

A windfarm generates 322 MW of electrical power.
The windfarm is connected to a transmission line at a potential difference of 132 kV.
Calculate the current from the windfarm. (3)

Answer 28

Current = power/voltage (1)
322 million/132,000 (1)
2439.4 (1)

Question 29

The windfarm produces 322 MW of power.
The windfarm is to be extended by adding 75 improved turbines. The extended windfarm will then produce a total of 539 MW.
Calculate the power produced by each improved turbine. (2)

Answer 29

539 - 322 = 217 (1)
217/75 = 2.9 (1)

Question 30

There is a plan to replace the existing transmission line from the windfarm with one at the higher potential difference of 400 kV.
The new transmission line will cross more than 200 km of mountains. The cables will hang 50 m above the ground from 600 new, taller pylons. Eventually, about 1000 of the old, shorter pylons will be removed.
Discuss the advantages and disadvantages of this plan. (6)

Answer 30

Social factors/economic factors
• people may not like it/pressure groups
• cost arguments

Environmental factors
• spoiled view/risk of birdstrike
• space for extra infrastructure eg. access roads/substations

Associated hazards
• danger from higher voltage
• dangers from construction work in mountainous area
• danger to maintenance crew from working at greater height

Energy efficiency arguments
• higher voltage leads to lower current
• lower current means reduced heat losses
• higher voltage means / lower current / can transmit energy further
• reduced heat loss means improved efficiency
Logical use of data
• taller pylons can be seen from further away
• net reduction in number of pylons / need to remove old ones
• stronger materials needed for pylons / cables • need for new transformers

Appropriate calculations
• 1000 - 600 = 400 fewer pylons (approx)
• current reduced by a factor of 132/400 (0.33)

Question 31

Electrical energy can be measured in… (1)

A amps
B kilowatt-hours
C volts
D watts

Answer 31

Kilowatt-hours

Question 32

Scientists are looking for new ways to produce electricity from renewable resources.
The diagram shows a model of a device to generate electricity from waves. The coil is fixed to the concrete block. The magnet can move freely inside the coil.
Explain how this device produces an electric current. (3)

Describe how the device can be altered to increase the electric current. (2)

Answer 32

Waves cause float to move up and down (1)
This causes magnet to move in and out of the coil (1)
Hence magnetic field of magnet (1)
Cuts across wire in coil (1)
Inducing a p.d. Across ends of coil (1)

Increase the number of turns on the coil (1)
Use a more powerful magnet (1)
Use full scale device (1)

Question 33

A way of producing electricity from a renewable source is tidal power. A dam is built across the mouth of a river.
Tidal water gets trapped behind the dam.
Which is used to generate electricity.
Discuss the advantages and disadvantages of using tidal power rather than other methods of generating electricity. (6)

Answer 33

Advantages of tidal power
• renewable energy source
• reduction in greenhouse gases/atmospheric pollution compared to fossil fuel)
• reduces reliance on fossil fuels
• conserves stocks of fossil fuels
• predictable source of energy
• regular/reliable supply of energy
• barrages at different areas would give energy supply at different times

Disadvantages of tidal power
• does not give continuous supply of energy
• destruction of plant/animal/bird habitats
• problems with passage of ships
• affects migration of fish
• high capital cost /very long payback time
• pollution caused from producing /transporting building materials
• visual pollution

Question 34

Eric pays 14p per kW h for electrical energy supplied by the National Grid. Calculate how much he could expect to save each year by using the energy from this wind turbine to heat and light the barn. (2)

Eric looks at the cost of installing the turbine. State how he should work out the payback time. (1)

Answer 34

0.14 x 6000 (1)
£840 (1)

Divide installation cost by annual saving (1)

Question 35

Eric’s chicks need to be kept warm at all times.
He uses halogen lamps to provide heat and light for most of the day. Eric thinks about changing his halogen lamps for energy saving lamps. Suggest why this might not actually be a benefit. (2)

Answer 35

Energy saving lamps would not transfer as much thermal energy (1)
He may have to use additional heating/lamps (1)

Question 36

There are several large-scale energy resources which are suitable alternatives to fossil fuels in some situations.
Two are: hydro-electric power and solar power.
Compare hydro-electric power with solar power as energy resources for the large-scale generation of electricity. (6)

Answer 36

• Both HEP and Solar power are renewable
• Both HEP and Solar power would save fossil fuels
• HEP only possible in some locations
• HEP requires reservoirs and damming of rivers
• This can damage environment /takes a lot of land out of use
• Energy from solar power installation is currently much less than energy from fossil fuel powered station
• Solar power only suitable in certain locations
• Solar power reliability dependent on constant sunshine
• Neither of them cause atmospheric pollution

Question 37

A kettle transfers ………………… energy to TE. (1)
A barbecue transfers ………….. energy to TE. (1)

Answer 37

Electrical (1)
Chemical (1)

Question 38

The blades of the fan are turned by an electric motor.
In 1 second, the motor gets 200 J of electrical energy from the mains supply. Only 180 J of this energy is used to turn the blades of the fan.
The rest of the energy is wasted.

(i) Calculate how much of the 200 J of energy is wasted. (1)
(ii) What happens to the wasted energy? (1)
(iii) Calculate the efficiency of the motor. (2)

Answer 38

20 (1)

Changed to thermal energy/heat (1)

180/200 x 100 (1)
90% (1)

Question 39

A man dropped an egg inside a padded box from a height.
He’s investigating to see if the padding stops the egg from breaking.
State the type of energy which the egg gains as it falls. (1)

Answer 39

Kinetic

Question 40

The weight of the egg is 0.6 N.
Calculate the work done on the egg to lift it up by 20 m. State the unit. (3)

Answer 40

0.6 x 20 (1)
12 (1)
J (1)

Question 41

Thevelocityofthecontainerwas18m/sasithitthefloor. The mass of the container was 0.5 kg.
Calculate the momentum of the container. (2)

Answer 41

0.5 x 18 (1)
9 (1)

Question 42

A student stands on the ground with an egg in his hand. He throws the egg vertically upwards.
The egg rises to a height of 10 m.
Then the egg falls and lands on the ground.
Describe the energy changes of the egg during this sequence of events. (6)

Answer 42

• chemical to kinetic while in his hand
• kinetic (gradually) to potential while rising from 0-10 m
• eventually all potential at 10 m with a little thermal (heat) energy
• some mention of conservation of energy
• potential (gradually) to kinetic as falls / 10 m-0
• with a little more thermal (heat) energy
• at 0 m sound energy
• at 0 m thermal (heat) energy

Question 43

A 60 kg student weighs 600 N. He does a bungee jump.
The bungee cord becomes straight and starts to stretch when he has fallen 50 m.

He first stops moving: (1)

A before all the energy has disappeared
B before the bungee cord starts to stretch
C when the bungee cord is stretched the most
D when the elastic potential energy is zero

When his speed is 10 m/s his momentum is: (1)
A 600 kg m/s
B 3000kgm/s
C 6000Nm/s
D 30000Nm/s

Answer 43

C (1)
A (1)

Question 44

A 60 kg student weighs 600 N. He does a bungee jump. The bungee cord becomes straight and starts to stretch when he has fallen 50 m.

State at what point in the bungee jump the student has maximum kinetic energy. (1)

Explain why his maximum kinetic energy is likely to be less than when the student falls 50m. (2)

Answer 44

After falling 50m/when cord is straight/starts to stretch (1)

Not all GPE is transferred to KE (1)
Some of the GPE transfers to TE/work is done (1)
Due to drag (1)

Question 45

Simon has a clock.
Once a week, Simon turns a key to tighten the spring. The spring uncoils slowly to keep the clock working.

Which type of energy is stored in the tightened spring? (1)

A chemical energy
B elastic potential energy
C gravitational potential energy
D thermal energy

Answer 45

Elastic potential energy

Question 46

Suggest what happens to the wasted energy in a clock (2)

Answer 46

Thermal/heat (1)
Energy is dissipated (1)
To the surroundings (1)

Question 47

A clock uses a pendulum.
The pendulum is a metal rod with a large mass at the end. The mass swings from side to side.
The spring keeps the pendulum swinging without stopping.
Describe the energy changes that happen as the pendulum continues to swing from side to side. (6)

Answer 47

Forms of energy:
• gravitational potential energy
• kinetic energy
• elastic potential energy
• heat(thermal) and sound

Location of energy:
• gravitational potential energy of mass as it rises
• kinetic energy of mass as it moves
• Elastic potential energy stored in spring
• Heat/sound dissipated to surroundings

Linked ideas:
• As the pendulum falls, gravitational potential energy changes to kinetic energy.
• the kinetic energy from the pendulum ends up as heat, warming the surroundings.
• the elastic potential energy in the clockspring becomes kinetic energy of the pendulum to keep the pendulum swinging.

Question 48

State why the pipes in a solar water heater are painted black. (1)

Answer 48

Black is a good absorber of heat/radiation

Question 49

A heater supplies 9000 J of thermal energy in 20 seconds. Calculate the power output of the heater.(2)

To produce the 9000 J of thermal energy, the heater needs 18000 J of energy from the Sun.
Calculate the efficiency of the solar water heater. (2)

Answer 49

9000/20 (1)
450 (1)

9000/18000 x 100 (1)
50% (2)