Energy Changes in a System (AQA GCSE Physics)

Exam Questions

2 hours15 questions
1a2 marks

A cyclist is riding along a straight, level road at a constant speed.

 

Complete the sentences with a suitable word or phrase.

 

As the cyclist rides along the road, energy in the .................................... energy store of the cyclist’s body decreases.

The speed of the cyclist is constant when the work done by the cyclist is .................................... the work done against air resistance.

 
1b1 mark
State the equation linking power (P), time (t) and work done (W).
1c3 marks
Calculate the work done by the cyclist when his power output is 350 W for 1500 seconds.

   

Work done = .................... J

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2a3 marks

Figure 1 shows how cavity wall insulation is installed in the wall of a house.

1-1-e-2a-cavity-wall-aqa-gcse-physics-sq-

Explain how the wall reduces unwanted energy transfers.
2b3 marks
Figure 2 shows a simplified layout of a non-condensing gas boiler that was typically used to heat houses in the United Kingdom. 

1-1-e-2b-boiler

Complete the following sentences describing the energy transfers taking place inside this system.

Choose answers from the box.

Each answer can be used once, more than once or not at all.

nuclear  thermal  chemical  magnetic


Energy is transferred from the .................................... energy store of the fuel to the ................................... energy store of the water and then to the ................................... energy store of the air.

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3a1 mark

Figure 1 shows a cell connected to a lamp. In a circuit, energy is transferred from the cell.

Figure 1

13-4-5

Which of the following units is the correct unit for energy?

Tick (✓) one box.

   

kg square
N square
J square
W square
J/kg square
3b3 marks

Complete the sentences.

Choose answers from the box.

Each answer can be used once, more than once or not at all.

nuclear chemical thermal

      

Energy is transferred from the  .............................. store of the cell, to the components.

Energy is transferred to the .............................. store of the lamp.

Energy is transferred from the lamp to the .............................. store of the surroundings.

3c1 mark
State the equation linking useful energy transfer output, total input energy transfer, and efficiency.
3d3 marks
60 J of energy is transferred from the cell to the lamp. 16 J is transferred from the lamp to the thermal store of the surroundings.



Calculate the efficiency of the lamp.

   

   

Efficiency  = .....................................

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4a1 mark

Figure 1 shows a toy car on a race track that performs a loop-the-loop.

1-1-e-4a-car-loop-track

At which point does the toy car have the most energy in its gravitational potential energy store?

Tick (✓) one box.

 

A B C D
square square square square

4b1 mark
State the energy transfer taking place between position A and position B.
4c4 marks

The toy car has 1.5 J of energy in its gravitational potential store at position A

Assuming that energy losses are negligible, state the energy in the car's kinetic store at B, then determine the speed of the car when it reaches position B.

The mass of the car is 400 g.

   

   

Speed = ................................... m/s
4d1 mark
In reality, there are energy losses in the system. 

 

The car's speed at position D will be less than its speed at position B.

State why this is the case.

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5a2 marks

Figure 1 shows a water slide called Verti-go at the water park, Aqualandia, in Spain.

1-1--e-5-a-verti-go---aqualandia-spain

Water is pumped down the slide to make the rider go faster.

Slide 1 is 28 m tall, and Slide 2 is 33 m tall.

 

This type of slide is called a 'freefall' water slide.


Suggest why it is given this name.

5b2 marks

What is the purpose of the water being pumped down the slide?

Tick (✓) two boxes.

   

To keep the riders cool in the sun square
To decrease friction square
To increase the gravitational potential energy of the riders square
To increase the speed of the riders square
To decrease the kinetic energy of the riders square
5c3 marks
The mass of one rider on Slide 2 is 50 kg. 
 

Calculate the change in gravitational potential energy as they climb the stairs and stand at the top of the slide, giving the units.

5d3 marks
Determine how much more gravitational potential energy the rider from part (c) has on Slide 2 than if they rode on Slide 1.

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1a1 mark

Figure 2 below shows a student doing a bungee jump from a stationary platform.

The bungee cord has an unstretched length of 30.0 m.

Figure 2

fig-2-medium-aqa-gcse-physics

The mass of the student is 60.0 kg.

The gravitational field strength is 9.8 N / kg.

Write down the equation which links gravitational field strength (g), gravitational potential energy (Ep), height (h) and mass (m).

1b3 marks
Using the equation from 1(a), calculate the change in gravitational potential energy from the position where the student jumps to the point 30.0 m below.

Give your answer to 3 significant figures.

1c1 mark

75% of this change in gravitational potential energy is transferred to the student’s kinetic energy store.

By how much does the student’s kinetic energy store increase after falling 30.0 m?


Kinetic energy gained = ________________________ J

1d4 marks
Calculate the speed of the student after falling 30.0 m.


Give your answer to two significant figures.

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2a2 marks
What is meant by specific heat capacity?
2b4 marks

Quenching is a process used to change the properties of steel by rapidly cooling it.

During the quenching process, the steel is heated to a very high temperature and then placed in a container of cold water.

A steel rod is quenched by heating it to a temperature of 815 °C before placing it in cold water.

The mass of the steel rod is 15 kg.

The final temperature of the rod and water is 60 °C.

Calculate the energy transferred from the steel rod to the water.

Use the correct equation from the Physics Equation Sheet.

Specific heat capacity of steel = 490 J/kg °C.

Give the answer to two significant figures.

2c3 marks

The temperature of the steel rod eventually returns to room temperature.

Compare the energies and movement of the particles in the steel rod and in the air at room temperature.

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3a3 marks

Figure 1 shows a person on a zip wire. The person's weight is 650 N.

1-1-3a-m-zip-wire

The person has 15 000 J in their gravitational potential store at the top of the tower.

Determine the vertical height of the tower.

Give your answer to 3 significant figures.

   

   

Vertical height of tower (3 significant figures) = .................................... m
3b3 marks
The height of the zip rope at the end of the ride is 2.5 m above ground. 
 

Determine the change in gravitational potential energy over the course of the zip rope ride.

3c2 marks
Determine the mass of the rider.



Give your answer to the nearest kg.

3d2 marks
Write down an expression relating energy in the kinetic store (E subscript k) and energy in the gravitational potential store (E subscript p).

State the amount of energy in the rider's kinetic store when the rider is at the end of the zip rope. 

You can assume frictional forces to be negligible.

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4a3 marks

Figure 1 shows a cyclist riding down an incline.

1-1-m-4a-cyclist

Complete the sentences. 



Choose answers from the box. 

Each answer can be used once, more than once or not at all.

thermal

nuclear

elastic potential

gravitational potential

kinetic

chemical

 

     

As the cyclist rides down the hill, the amount of energy in his .............................. store decreases.

   

As the cyclist accelerates, energy in his .............................. store increases.

   

When the cyclist uses his breaks to stop, energy is transferred to the .............................. store of the brake pads.

4b3 marks

In one journey, the cyclist applies his brakes.

The break pads increase in temperature from 13°C to 51°C.

The material of the break pads has a specific heat capacity of 517 J/kg °C.

The mass of the break pads is 0.043 kg

Calculate the change in thermal energy of the break pads.

Give your answer to 3 significant figures.

   

   

Change in thermal energy (3 significant figures) = .................... J
4c4 marks

The cyclist descends the hill on another journey, this time without braking.

The hill the cyclist rode down has a vertical height of 23.5 m.

20 kJ of energy was transferred from the cyclist's gravitational potential energy store as he rode from the top of the hill to the bottom.

Determine the mass of the cyclist.

Give your answer to 3 significant figures.

   

   

Mass of cyclist (3 significant figures) = .................................... kg
4d4 marks

Calculate the maximum speed of the cyclist during his descent.

Assume now that there are no energy losses.

Give your answer to 1 significant figure.

   

Maximum speed (1 significant figure) = .................................... m/s

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5a6 marks

A group of students carry out an investigation into the specific heat capacity of water. 

Figure 1 shows the equipment the students use.

1-1-m-5a-specific-heat-capacity-equipment

Describe a method the students could use to determine the specific heat capacity of water.

5b1 mark
State the purpose of insulating the beaker of water.
5c1 mark
The students noticed that when the power supply was turned on, the water did not immediately begin to heat up.



Suggest one reason why.

5d3 marks

The energy transferred to the heater in 600 s was 36 050 J.

The temperature of the water increased by 17°C.

The specific heat capacity of water is 4200 J/kg °C.

Determine the mass of water the students used.

   

   

Mass of water = .................................... kg

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1a3 marks

The diagram in Figure 1 below shows a wind turbine.

Figure 1

turbine

The relationship between the power output of the turbine and the kinetic energy of the air passing the blades each second is directly proportional.

 

Describe the change to the power output when the wind speed is reduced by half.
1b4 marks
During a moderate breeze, the mass of air passing the wind turbine each second is 14 000 kg.

 

Calculate the speed of the air passing the blades each second if the power output of the wind turbine is 400 kW.

You can assume that the process is 100% efficient.

 
 
Speed of air = .................................... m/s 

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25 marks

Figure 3 shows a rollercoaster.

Figure 3

rollercoaster

The rollercoaster car is raised to a height of 40m in 35 seconds by an electric motor.

The mass of the rollercoaster and passengers is 550 kg.

The motor has a power rating of 10 000 W.

Gravitational field strength = 9.8 N / kg.

 

Calculate the efficiency of the motor.
 
 
 
Efficiency = ....................................

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3a4 marks

The CPU (Central Processing Unit) in a desk-top computer controls most of the functions of the computer. 

Modern CPUs generate large amounts of heat. 

Specially designed cooling units such as the one shown in Figure 1 are used to dissipate this heat away from the CPU.

This is to prevent it from overheating and being damaged.

1-1-h-3b-cpu-aqa-gcse-physics-sq

Energy is transferred from the CPU through the metal base of the cooling unit

Explain how this process occurs.
3b2 marks
The CPU cooling unit has metal fins that are designed to transfer energy quickly to the surroundings.

 

State two features that would help the metal cooling fins to transfer energy quickly to the surroundings.

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4a5 marks

Salmon are born in freshwater rivers, spend most of their lives in the sea, but return to freshwater rivers to breed. As they swim up rivers, they often have to jump up waterfalls.

Figure 1 shows a salmon attempting to jump up a waterfall with a vertical height of 0.36 m.

Figure 1

1-7-4a-h-salmon-waterfall-energy

The salmon has a mass of 1.84 kg.

The salmon leaves the water with a speed of 3.2 m/s.

Determine whether the salmon can make the height required for the jump.

4b3 marks

Another salmon of mass 2.2 kg tries to make the jump. 

Calculate the minimum speed with which the salmon would have to leave the water in order to reach the height required.

   

   

Minimum speed  = .................................... m/s
4c2 marks
The salmon swim further upstream and encounter a waterfall that is much higher than the previous one.


The salmon attempts the jump, but fails, and performs a somersault during the descent. The salmon straightens out before it enters the water as shown in Figure 2.

Figure 2

salmon

Discuss whether the speed of entry into the water is greater than, less than or equal to the speed with which it leaves the water. Ignore any effects of air resistance.

4d1 mark
The temperature of the water at the bottom of a waterfall is greater than the temperature of the water at the top. 



Suggest why this is the case.

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5a3 marks

Figure 1 shows a student at two stages of a bungee jump.

1-1-h-5a-bungee

Complete the sentences. 

Choose answers from the box. 

Each answer can be used once, more than once or not at all.

elastic potential

kinetic

gravitational potential

electrostatic

chemical

magnetic

 

     

Before the student jumps, they have energy in their .............................. store.

   

As the student falls, energy is transferred to their  .............................. store.

   

At the bottom of the jump, the bungee cord stretches and energy is transferred to the .............................. store of the rope.

5b4 marks
At the lowest point of the jump, the student is momentarily stationary. At the lowest point of the jump, the length of the bungee cord is 82 m. The unstretched length of the cord is 40 m.

The bungee cord acts like a spring with a spring constant of 45 N/m.

Calculate the energy stored in the bungee chord at the lowest point of the jump.

Include the correct unit in your answer.

Use the correct equation from the Physics Equations Sheet.

   

   

Energy = ..................................... Unit = ....................................
5c4 marks

Determine the mass of the student.

 

You may assume there are no energy losses in the system.

5d5 marks
Determine the speed of the student at the point in the jump where the bungee cord is at its maximum unstretched length.
 

You can assume air resistance is negligible.

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