Energy stores & systems

A person performs a ‘vertical box jump’.

Figure 4 shows five different stages, A, B, C, D and E, of the jump.

Complete the sentences.

Choose answers from the box.

The person in Figure 4 has a mass of 60 kg.

The person leaves the ground with a speed of 5.5 m/s.

Calculate the kinetic energy of the person.

Use the equation:

kinetic energy = 0.5 × mass × (speed)²

The person has a mass of 60 kg.

The height of the jump is 1.5 m.

gravitational field strength = 9.8 N/kg

Calculate the gravitational potential energy of the person at a height of 1.5 m.

Use the equation:

gravitational potential energy = mass × gravitational field strength × height

The person jumps onto a box higher than the one in Figure 4, on page 12.

To jump onto a higher box, the person’s speed when leaving the ground is different.

Explain how the speed is different when jumping onto a higher box.

You should answer in terms of gravitational potential energy and kinetic energy.

Suggest one reason why a person is more likely to be injured when falling off a higher box.

Fossil fuels are burned in car engines and in power stations.

Describe how different energy stores change in a car engine when a fossil fuel is burned.

Some car engines burn a fuel that is produced using plants.

Name a fuel produced using plants.

Some cars do not contain an engine that burns a fuel.

Suggest how cars that do not burn a fuel are powered.

Figure 6 shows how the total amount of electricity generated in the UK has changed with time.

The proportion of electricity that is generated using renewable energy resources has increased since the year 2013.

Which conclusion is correct?

Use Figure 6.

Tick () one box.

The UK plans to stop burning fossil fuels to generate electricity.

Explain one reason why it will take many years before all electricity is generated using renewable resources.

Renewable energy resources can have a negative impact on the environment.

Give one negative environmental impact of hydro-electric power and of wind power.

Hydro-electric power

Fossil fuels are burned in car engines and in power stations.

Describe how different energy stores change in a car engine when a fossil fuel is burned.

Some car engines burn a fuel that is produced using plants.

Name a fuel produced using plants.

Some cars do not contain an engine that burns a fuel.

Suggest how cars that do not burn a fuel are powered.

Figure 1 shows how the total amount of electricity generated in the UK has changed with time.

The proportion of electricity that is generated using renewable energy resources has increased since the year 2013.

Which conclusion is correct?

Use Figure 1.

Tick () one box.

The UK plans to stop burning fossil fuels to generate electricity.

Explain one reason why it will take many years before all electricity is generated using renewable resources.

Renewable energy resources can have a negative impact on the environment.

Give one negative environmental impact of hydro-electric power and of wind power.

Hydro-electric power

Figure 10 shows an electric whisk that plugs into the mains electricity supply.

The whisk can mix food by spinning a beater.

Give two energy stores that increase when the whisk is switched on.

Use the Physics Equations Sheet to answer questions 06.2 and 06.3.

Work is done by the whisk when it is used to mix food.

Write down the equation that links power (P), time (t) and work done (W).

The power output of the whisk is 92 W.

Calculate the time for the whisk to do 23 000 J of work.

Use the Physics Equations Sheet to answer questions 06.4 and 06.5.

Which equation links current (I), power (P) and resistance (R)?

Tick (✓) one box.

The current in the whisk is 500 mA.

The resistance of the whisk is 640 Ω.

Calculate the power of the whisk.

The whisk has several settings that allow the beater to spin at different speeds.

A faster beater speed needs a greater power input from the mains electricity supply.

What is the potential difference between the live wire and neutral wire in the mains electricity supply?

Changing the beater speed does not change the potential difference between the live wire and neutral wire.

The power input to the whisk changes because the current in the whisk changes.

Complete the sentence.

When the beater speed increases, the current in the whisk increases because the

A drone is a miniature aircraft that has a remote control.

An inventor designed a battery powered drone.

The inventor tested what would happen if the battery runs out of charge during a flight.

Figure 5 shows the inventor about to launch the drone.

After the drone was launched, it moved at a constant speed and gained height.

The thermal stores of energy of the drone increased.

Describe two other changes to the energy stores of the drone as it moved at a constant speed and gained height.

When the drone reached a height of 840 m the motor was switched off.

The motor was switched back on after a short time, when the drone had fallen to a lower height above the ground.

The change in gravitational potential energy of the drone during the fall to this lower height was 3920 J.

The mass of the drone is 2.5 kg.

gravitational field strength = 9.8 N/kg

Calculate the height above the ground of the drone when the motor was switched back on.

Use the Physics Equations Sheet.

When the motor was switched off, the kinetic energy of the drone was 150 J.

Calculate the maximum possible speed of the drone when the motor was switched back on.

Use the Physics Equations Sheet.

Give your answer in km/s.

A trampoline is made from a sheet of material held in place by stretched springs. Figure 5 shows a child on a trampoline.

Position A shows the child’s maximum height above the trampoline. Position B shows the lowest position reached by the child when landing on the trampoline. Describe the changes to the stores of energy of the:

• child

• springs

• surroundings

as the child moves from position A to position B. Child

When the child is at position A, each trampoline spring is stretched by 0.056 m The elastic potential energy of each spring is 4.9 J When the child is at position B, the elastic potential energy of each spring increases to 8.1 J Calculate the extension of each spring when the child is at position B. Use the Physics Equations Sheet.

As the child bounces on the trampoline the child does work. What is the work done by the child equal to? Tick (✓) one box.

An eco-house is designed to be environmentally friendly. Figure 4 shows a picture of an eco-house.

The solar panels and a wind turbine are used to generate electricity for the eco-house. Solar and wind are both renewable energy resources. What does renewable energy resource mean? Tick (✓) one box.

Biomass, nuclear and natural gas are three other energy resources. Complete the table to show whether each energy resource is renewable or non-renewable.

Moving air makes the wind turbine spin. The wind turbine generates electricity which is used to charge a battery. Complete the sentences. Choose answers from the box.

energy.

battery.

The roof of the eco-house is covered with soil. Covering the roof with soil decreases the thermal conductivity of the roof. What are the advantages of having a roof with a lower thermal conductivity? Tick (✓) two boxes.

The average power transferred to the solar panels by sunlight is 26 000 W Calculate the average energy transferred to the solar panels in 30 seconds. Use the equation: energy transferred = power × time

Write down the equation that links efficiency, total power input and useful power output.

The solar panels on the roof of the eco-house have an efficiency of 0.15 The average power input to the solar panels is 26 000 W Calculate the average useful power output from the solar panels.

Explain why it is a good idea for the eco-house to have both a wind turbine and solar panels.

Figure 5 shows a wood-fired hot tub.

What type of fuel is wood? Tick (✓) one box.

Give two environmental effects of using wood as an energy resource.

Describe the change to the stores of energy of the wood, pipe and water as the water is heated.

The temperature of the water reaches 42 °C The temperature then stays constant even though the fire continues to burn. Explain why the temperature of the water stays constant.

Figure 3 shows a mobile phone being recharged by a portable power source.

Why does the battery in the phone need recharging?

Tick one box.

The power source provides a current of 1.86 A at a potential difference of 3.90 V

Calculate the power of the power source.

Use the equation:

power = potential difference × current

Choose the correct unit from the box.

A student needs a new power source.

Figure 4 shows three different sized power sources.

Table 1 gives data about the different power sources.

The student chose the large power source.

Suggest why the student chose the large power source.