Energy stores and systems

Figure 10 shows a toy which is hung from a support.

When the handle is pulled down and then released, the toy bounces up and down.

When the handle is pulled down, the spring extends.

The extension of the spring is 0.35 m.

The spring constant of the spring is 5.6 N/m.

Calculate the elastic potential energy stored by the stretched spring.

Use the equation:

elastic potential energy = 0.5 × spring constant × (extension)²

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

Which equation links gravitational field strength (g), gravitational potential energy (E_p), height (h) and mass (m)?

Tick () one box.

When the handle is released, the toy moves upwards through a height of 0.60 m.

The toy has 0.294 J of gravitational potential energy in its highest position.

gravitational field strength = 9.8 N/kg

Calculate the mass of the toy.

Figure 11 shows the toy in three different positions.

The toy is released from position A and moves upwards.

The toy is moving upwards in position B.

The toy is at maximum height in position C.

Between position A and position B, the extension of the spring decreases.

How does the elastic potential energy stored by the spring change as the extension decreases?

Tick () one box.

Between position B and position C, the toy slows down.

How does the kinetic energy of the toy change as the toy slows down?

Tick () one box.

How does the gravitational potential energy of the toy change as the toy moves from position B to position C ?

Tick () one box.

The toy moves up and down many times before eventually stopping.

Which two of the following are reasons why the toy eventually stops?

Tick () two boxes.

Figure 12 shows a device that accelerates a toy car at the start of a race track.

Pulling the handle compresses the spring in the device by 0.075 m.

When the handle is released, the energy stored in the compressed spring is transferred to the toy car.

spring constant = 64 N/m

mass of toy car = 0.052 kg

Calculate the maximum possible speed of the toy car just after the car starts to move.

Use the Physics Equations Sheet.

Give your answer to 2 significant figures.

Figure 13 shows the path of the toy car along a loop section of the race track.

The car moves along the track from position A to position B and then to position C.

Describe how the energy stores of the car change as the car moves along the track from position A to position C.

Ignore the effects of friction and air resistance.

At the end of the race track, the toy car passes through a light gate that measures the speed of the car.

Which two measurements are needed to determine the speed of the car?

Tick () two boxes.

Figure 16 shows a wind turbine.

Wind turbines may generate electricity when the electricity is not needed.

Two methods that can be used to store the energy from the turbine are:

Method A: Heating water to a high temperature.

Method B: Pumping water uphill into a reservoir.

Which energy store increases when water is heated?

Which energy store increases when water is pumped uphill into a reservoir?

Table 4 shows information about the two methods of storing energy.

Compare the advantages and disadvantages of the two methods of storing energy.

Include calculations in your answer.

Decreasing the amount of carbon dioxide released by different activities will help slow down climate change.

Transport and generating electricity are the two activities that released the largest amounts of carbon dioxide in the UK in 2018.

Explain one change that would reduce the amount of carbon dioxide released by each activity.

Generating electricity

Figure 1 shows a wind turbine.

Wind turbines may generate electricity when the electricity is not needed.

Two methods that can be used to store the energy from the turbine are:

Method A: Heating water to a high temperature.

Method B: Pumping water uphill into a reservoir.

Which energy store increases when water is heated?

Which energy store increases when water is pumped uphill into a reservoir?

Table 1 shows information about the two methods of storing energy.

Compare the advantages and disadvantages of the two methods of storing energy.

Include calculations in your answer.

Decreasing the amount of carbon dioxide released by different activities will help slow down climate change.

Transport and generating electricity are the two activities that released the largest amounts of carbon dioxide in the UK in 2018.

Explain one change that would reduce the amount of carbon dioxide released by each activity.

Generating electricity

Figure 8 shows a student before and during a bungee jump.

The diagram is not to scale.

In position B, the student is moving towards the river and the bungee cord is stretching.

How do the energy stores in position B compare with the energy stores in position A ?

Tick (✓) one box in each row.

The bungee cord behaves like a spring with a spring constant of 78.4 N/m.

At one point in the bungee jump, the extension of the bungee cord is 25 m.

Calculate the elastic potential energy stored by the bungee cord.

Use the equation:

elastic potential energy = 0.5 × spring constant × extension²

Table 5 shows information about different bungee cords.

Bungee cord C will have a smaller extension than A or B for any bungee jumper.

Give the reason why.

Which bungee cord would be safest to use for a person with a large weight?

Give a reason for your answer.

A baby bouncer is a harness attached to a spring that hangs from a door frame. Figure 7 shows a baby in a baby bouncer in two positions.

The baby bouncer should not be used with babies that have a mass greater than 12 kg. Suggest one reason why.

In positions A and B the baby is stationary. Describe the energy transfers as the baby moves from position A to position B.

In one position the extension of the spring is 8.0 cm. The elastic potential energy stored by the spring is 4.0 J. Calculate the spring constant of the spring. Use the Physics Equations Sheet.

Figure 1 shows a boy bouncing on a trampoline.

The boy falls from the position in Figure 1 towards the trampoline.

Complete the sentences.

Choose answers from the box.

As the boy lands on the trampoline, each spring stretches 0.015 m.

spring constant of each spring = 120 000 N/m

Calculate the energy stored by each spring.

Use the equation:

elastic potential energy = 0.5 spring constant (extension)²

There are 40 springs on the trampoline.

Calculate the total energy stored by the 40 springs when each spring is stretched by 0.015 m.

Use your answer from Question 01.2

The kinetic energy of the boy as he lands on the trampoline is 600 J.

The maximum kinetic energy of the boy after he bounces is 45% of his kinetic energy as he lands.

Calculate the maximum kinetic energy of the boy after he bounces.

Why is the kinetic energy of the boy after he bounces less than his kinetic energy as he lands?

Tick (✓) one box.

Figure 11 shows a student launching a toy aeroplane. To launch the aeroplane, the student pulls on it to stretch the spring and then releases it.

Just before the toy aeroplane is released, the spring has an extension of 0.12 m. mass of aeroplane = 0.020 kg spring constant of the spring = 50 N/m Calculate the maximum speed of the toy aeroplane just after it is launched. Use the Physics Equations Sheet. Give the unit.

Complete the sentence. As the aeroplane moves upwards through the air there is a decrease in the energy of the aeroplane.

Give one factor which would increase the distance the toy aeroplane travels horizontally before hitting the ground.

Figure 11 shows a diver about to dive off a diving board.

Complete the sentences.

Choose answers from the box.

elastic potential gravitational potential kinetic nuclear

As the diver falls towards the water there is a decrease in

her energy.

As the diver falls towards the water there is an increase in

her energy.

Write down the equation which links kinetic energy (E_k), mass (m) and speed (v).

At the instant the diver hits the water, the kinetic energy of the diver is 5040 J.

The speed of the diver is 12 m/s.

Calculate the mass of the diver.

Most of the kinetic energy of the diver is transferred to the water.

How does this affect the thermal energy of the water?

Tick (✓) one box.

Electric cars have motors that are powered by a battery.

Diesel cars have engines that are powered by diesel fuel.

Table 2 compares one type of electric car with one type of diesel car.

The electric car has a range of 400 km with a fully charged battery.

The diesel car has a range of 1120 km with a full tank of diesel.

Explain the difference in the time needed to complete a 500 km journey using the electric car compared with the diesel car.

Assume both cars travel at the same speed.

Energy density is the amount of energy stored per kilogram of the energy source.

Show why the diesel car has a greater range than the electric car.

Use data from Table 2.

Assume the efficiency of the two cars is the same.

Include calculations in your answer.

Engineers have developed a way of charging electric cars while they are driving along the road.

Coils of wire buried under the road transfer energy to the car’s battery as the car is passing over the coils.

Figure 6 shows a charging lane on a motorway.

Suggest two advantages of using this method to charge electric cars compared with plugging them into the mains electricity supply.

When electric cars are not being driven, energy stored in their batteries could be used to meet sudden peaks in electricity demand.

Suggest how.

Figure 1 shows a cyclist riding along a flat road.

Complete the sentence.

Choose answers from the box.

chemical elastic potential gravitational potential kinetic

the cyclist increases.

The mass of the cyclist is 80 kg. The speed of the cyclist is 12 m/s.

Calculate the kinetic energy of the cyclist.

Use the equation: kinetic energy = 0.5 × mass × (speed)²

When the cyclist uses the brakes, the bicycle slows down.

This causes the temperature of the brake pads to increase by 50 °C. The mass of the brake pads is 0.040 kg. The specific heat capacity of the material of the brake pads is 480 J/kg °C.

Calculate the change in thermal energy of the brake pads.

Use the equation:

change in thermal energy = mass × specific heat capacity × temperature change

How is the internal energy of the particles in the brake pads affected by the increase in temperature?

Tick one box.

Figure 5 shows a cyclist riding along a straight, level road at a constant speed.

Complete the sentences.

in the cyclist’s body decreases.

The speed of the cyclist is constant when the work done by the cyclist is

Figure 6 shows how the speed changes as the power output of the cyclist changes.

Write down the equation that links power, time and work done.

Calculate the work done by the cyclist when his power output is 200 W for 1800 seconds.

Calculate the percentage increase in speed of the cyclist when the power output changes from 200 W to 300 W.

The maximum speed this cyclist can travel on a level road is 14 m/s.

How does cycling uphill affect the maximum speed of this cyclist?

Explain your answer.