AQA AS Physics

Topic Questions

4.6 Work, Energy & Power

11 mark

The equation to calculate the work done by an object is given as:

W = F s

What quantity is represented by the symbol s?

  • seconds

  • speed

  • displacement

  • time

Did this page help you?

21 mark

Which line, A to D, in the table correctly shows the units for power and efficiency?

  Power Efficiency
A

No unit

W

B

No unit

J

C J

No unit

D

W

No unit

Did this page help you?

31 mark

Which line, A to D, in the table correctly shows whether work done and power are scalar or vector quantities?

  Work done Power
A

scalar

scalar

B

vector

vector

C

scalar

vector

D

vector

scalar

Did this page help you?

41 mark

Which of the following equations is incorrect?

  • powerfraction numerator w o r k space d o n e over denominator t i m e end fraction

  • power = fraction numerator e n e r g y space t r a n s f e r r e d over denominator t i m e end fraction

  • power = force  × displacement

  • power = force × velocity

Did this page help you?

51 mark

A block slides from rest down a rough slope from the top to the bottom, as shown below.

q5_work-energy-_-power_aqa-as-physics-mcq

Which of the following equations shows the correct energy conservation as the block slides from the top of the slope to the bottom of the slope?

  • loss of gravitational potential energy = gain in kinetic energy

  • loss of gravitational potential energy = gain in kinetic energy + work done against friction

  • loss of gravitational potential energy + work done against friction = gain in kinetic energy 

  • loss of gravitational potential energy + gain in kintetic energy = work done against friction

Did this page help you?

61 mark

Which of the following statements correctly gives the law of conservation of energy?

  • Energy can be created but not destroyed

  • Cannot be created, destroyed or transferred from one form to another

  • Energy cannot be created or destroyed, but it can be transferred from one form to another 

  • Energy cannot be created, but it can be destroyed or transferred from one form to another

Did this page help you?

71 mark

A skydiver of mass 62 kg jumps from a plane flying at an altitude of 4500 m.  They deploy the parachute when they are 600 m from the ground.

How much gravitational potential energy does the skydiver lose before they deploy the parachute?

  • 2.42 × 105 J

  • 3.65 × 105 J

  • 2.37 × 106 J

  • 2.73 × 106 J

Did this page help you?

81 mark

Which of the following graphs shows the variation of gravitational potential energy, Ep with height, h, as an elevator ascends from the bottom floor of a building to the top floor?

q8_work-energy-_-power_aqa-as-physics-mcq

Did this page help you?

91 mark

A car of mass 950 kg accelerates from 2.5 m s–1 to 4.8 m s–1.

What is the gain in kinetic energy of the car?

  • 8.40 J

  • 2510 J

  • 7980 J

  • 16 000 J

Did this page help you?

101 mark

A force – displacement graph is shown below.

q10_work-energy-_-power_aqa-as-physics-mcq

What does the shaded area represent?

  • work done

  • displacement

  • power

  • efficiency

Did this page help you?

11 mark

To exit an underground cave network, an electric winch is used to raise a lift containing the cavers back to the surface.  A diagram of the setup is shown below.

q21_work-energy-_-power_aqa-as-physics-mcq

The lift and the cavers have a total mass of 400 kg.  The winch raises the lift through a vertical height of 1000 m in 2 minutes.

If the motor is 80% efficient, what is the total power wasted by the winch?

  • 0.83 kW

  • 0.67 kW

  • 8.2 kW

  • 490 kW

Did this page help you?

21 mark

A child on a swing is released from rest at position A.  They were found to be moving at 2.2 m s–1 at position B.  The mass of the child and the swing is 28 kg.  The rope connecting the swing to the frame is 1.6 m.  The positions A and B are shown below.

q22_work-energy-_-power_aqa-as-physics-mcq

There is a constant resistive force acting on the child between A and B.

What is the resistive force acting on the child between A and B?

  • 38.1 N

  • 48.5 N

  • 232 N

  • 296 N

Did this page help you?

31 mark

Water flows from a lake into a turbine that is a vertical distance of 90 m below the lake, as shown.

q23_work-energy-_-power_aqa-as-physics-mcq

The mass flow rate of the water is 2400 kg min–1. The turbine has an efficiency of 75%.

What is the output power of the turbine?

  • 26 kW

  • 35 kW

  • 1.6 MW

  • 2.1 MW

Did this page help you?

41 mark


When the 4 kg mass is released from rest at a height of 5 m it falls to the ground pulling the 3 kg mass up the slope.  The rough surface of the ramp provides a constant frictional force of 2 N.

q24_work-energy-_-power_aqa-as-physics-mcq

What speed will the 4 kg mass hit the ground?

  • 5.80 m s–1

  • 7.29 m s–1

  • 9.90 m s–1

  • 11.3 m s–1

Did this page help you?

51 mark

A stone of mass 1.2 kg is dropped from a height of 15 m above the surface of a thick, oily liquid, as shown below.  The surface of the liquid is 2 m above the ground. 

q25_work-energy-_-power_aqa-as-physics-mcq

The resistive force acting on the stone as it falls through the liquid is 150 N. 

What is the speed of the stone when it has travelled 0.5 m through the liquid?

  • 8.16 m s–1

  • 10.7 m s–1

  • 13.4 m s–1

  • 16.8 m s–1

Did this page help you?

61 mark

The diagram shows a lift system in which the elevator (mass m1) is partly counterbalanced by a heavy weight (mass m2)

q26_work-energy-_-power_aqa-as-physics-mcq

At what rate does the motor provide energy to the system when the elevator is rising at a steady speed v? (g = acceleration of free fall)

  • 1 half m subscript 1 v squared

  • 1 half left parenthesis m subscript 1 minus m subscript 2 right parenthesis v squared

  • m subscript 1 g v

  • left parenthesis m subscript 1 minus m subscript 2 right parenthesis g v

Did this page help you?

71 mark

The diagram shows the design of a water wheel which drives a generator to produce electrical energy. The flow rate of the water is 200 kg s–1. The generator supplies a current of 32 A at a voltage of 230 V.

q27_work-energy-_-power_aqa-as-physics-mcq

Ignoring any changes in kinetic energy of the water, what is the efficiency of the system?

  • 14 %

  • 16 %

  • 22 %

  • 47 %

Did this page help you?

81 mark

A bungee jumper has 24 kJ of gravitational potential energy at the top of his jump. He is attached to an elastic rope which starts to stretch after a short time of free fall. Assume that energy loss through air resistance is negligible.

 

GPE / kJ

EPE / kJ

KE / kJ

Top

24

0

0

Bottom

0

24

0

What are the possible values when the jumper is half–way down?

 

GPE / kJ

EPE / kJ

KE / kJ

A 12 10 2
B 12 8 4
C 8 8 8
D 12 2 10

Did this page help you?

91 mark

An engineer is preparing to install a new escalator for an underground train company.  For their calculations, they assume that the average mass of a passenger using the escalator is 70 kg. 

The escalator will be installed at an angle of 30o to the horizontal and lift people to a vertical height of 15 m in 10 seconds, as shown below.

q29_work-energy-_-power_aqa-as-physics-mcq

If all of the passengers stand still on the escalator, 75 people can step on at the bottom and off at the top in each minute. 

When the escalator is fully laden with passengers the motor driving the escalator is 80% efficient and the frictional force acting on the escalator system 15 kN.

What is the input power needed to operate the motor?

  • 9.6 kW

  • 16 kW

  • 20 kW

  • 25 kW

Did this page help you?

101 mark

Wind turbines are becoming increasing popular for generating electricity.  On average they have are 70% efficient at producing electrical energy.  In one particular design of wind turbine the blades rotate about a horizontal axis and sweep out at an area of 1400 m2.

On a particular day the horizontal axis of the turbine blades points directly into the wind, as shown below, and the wind speed is 15 m s–1.  The air is slowed to 13 m s–1 after passing through the turbine blades.  

q30_work-energy-_-power_aqa-as-physics-mcq

How many wind turbines would be needed to produce the same amount of electricity as a 1000 GW power station?

Assume that there are no frictional forces in the turbine and take the density of air to be is 1.2 kg m–3

  • 504

  • 671

  • 1056

  • 2025

Did this page help you?

11 mark

Trains supply coal to a power station. The table below gives quantities describing the operation of the power station.

 

symbol

unit

power station output

P

W

number of trains per day

N

 

mass of coal on a train

M

kg

energy from 1 kg of coal

J

J

number of seconds in one day

S

s

Which expression gives efficiency of the power station?

  • fraction numerator P S over denominator N M J end fraction

  • fraction numerator P S N over denominator M J end fraction

  • fraction numerator N M J over denominator P S end fraction

  • fraction numerator N M over denominator P S J end fraction

Did this page help you?

21 mark

Initially, four identical uniform blocks, each of mass m and thickness h, are spread on a table.

q12_work-energy-_-power_aqa-as-physics-mcq

How much work is done on the blocks in stacking them on top of one another?

  • 3 space m g h

  • 6 space m g h

  • 8 space m g h  

  • 10 space m g h

Did this page help you?

31 mark

The first column in the table gives four examples of work being done. The second column gives more detail of the action.

Which row is not correct?

 

Example

Detail

A

a diver dives from a diving board into a swimming pool

work is done by the diver against gravity as she falls

B

a person pushes a car along a level road

work is done by the person against friction

C

an electron is accelerated towards a positively–charged plate

work is done on the electron by the electric field of the plate

D

a piston is pushed outwards as a gas expands

work is done on the atmosphere by the gas

Did this page help you?

41 mark

The data below are taken from a test of a petrol engine for a motor car.

         power output                150kW

         fuel consumption                  20 litres per hour

       energy content of fuel                 40 MJ per litre

Which expression will evaluate the efficiency of the engine?

  • fraction numerator 150 cross times 10 cubed over denominator 40 cross times 10 to the power of 6 cross times 20 cross times 60 cross times 60 end fraction

  •  fraction numerator 150 cross times 10 cubed cross times 60 cross times 60 over denominator 20 cross times 40 cross times 10 to the power of 6 end fraction

  •  fraction numerator 150 cross times 10 cubed cross times 40 cross times 10 to the power of 6 cross times 20 over denominator 60 cross times 60 end fraction

  • fraction numerator 150 cross times 10 cubed cross times 20 over denominator 40 cross times 10 to the power of 6 cross times 60 cross times 60 end fraction

Did this page help you?

51 mark

A weight W hangs from a trolley that runs along a rail. The trolley moves horizontally through a distance p and simultaneously raises the weight through a height q.

q15_work-energy-_-power_aqa-as-physics-mcq

As a result, the weight moves through a distance r from X to Y. It starts and finishes at rest.

How much work is done on the weight during this process?

  • Wp

  • W(p + q)

  • Wq

  • Wr

Did this page help you?

61 mark

A uniform solid block has weight 500 N, width 0.4 m and height 0.6 m. The block rests on the edge of a step of depth 0.8 m, as shown.

q16_work-energy-_-power_aqa-as-physics-mcq

The block is knocked over the edge of the step and rotates through 90° before coming to rest with the 0.6 m edge horizontal.

What is the change in gravitational potential energy of the block?

  • 300 J

  • 400 J

  • 450 J

  • 550 J

Did this page help you?

71 mark

A body travelling with a speed of 20 m s–1 has kinetic energy Ek.

If the speed of the body is increased to 80 m s–1, what is its new kinetic energy?

  • 4 E subscript k

  • 8 E subscript k

  • 12 E subscript k

  • 16 E subscript k

Did this page help you?

81 mark

A concrete cube of side 0.60 m and uniform density 2.0 × 103 kg m–3 is lifted 5.0 m vertically by a crane.

What is the change in potential energy of the cube?

  • 0.75 kJ

  • 7.4 kJ

  • 21 kJ

  • 470 kJ

Did this page help you?

91 mark

A steel ball is falling at constant speed in oil.

Which graph shows the variation with time of the gravitational potential energy Ep and the kinetic energy Ek of the ball?

q19_work-energy-_-power_aqa-as-physics-mcq

Did this page help you?

101 mark

Car X is travelling at half the speed of car Y. Car X has twice the mass of car Y.

Which statement is correct?

  • car X has half the kinetic energy of car Y

  • car X has one quarter of the kinetic energy of car Y

  • car X has twice the kinetic energy of car Y

  • the two cars have the same kinetic energy

Did this page help you?