Energy – Forces Doing WorkEdexcel GCSE Physics: Topic test

20 questions, 54 marks

Edexcel GCSE Physics

Energy – Forces Doing Work topic test

Total 54 marks

Name

Class

Date

1
A removals worker pushes a sofa a distance of 6 m across a level driveway by applying a constant horizontal force of 60 N. The sofa moves in the same direction as the applied force throughout.
(a)
Which equation correctly relates the work done by the worker's force to the force applied and the distance moved?
[1 mark]
Awork done = force ÷ distance moved
Bwork done = force × distance moved in the direction of the force
Cwork done = force × time taken
Dwork done = distance moved ÷ force
(b)
As the worker does work pushing the sofa, what happens to the energy transferred?
[1 mark]
AEnergy transferred (J) is equal to the work done (J)
BEnergy is destroyed as the work is done
CNo energy is transferred unless the sofa is lifted vertically
DEnergy transferred is always exactly double the work done
(c)
Calculate the work done by the worker in pushing the sofa 6 m with a force of 60 N, showing your working and stating the correct unit.
[2 marks]
Total for question 1: 4 marks
2
A construction crane lifts a steel beam of mass 250 kg vertically upwards through a height of 12 m at a steady speed, taking 20 s to complete the lift. Assume the gravitational field strength is g = 10 N/kg.
(a)
Which quantity increases as the crane raises the beam to a greater height, assuming the beam's speed and mass stay constant?
[1 mark]
AThe beam's mass
BThe gravitational field strength acting on the beam
CThe beam's gravitational potential energy
DThe beam's kinetic energy, which increases without limit
(b)
The crane's motor does work against gravity in lifting the beam at a steady speed. What is this work done against gravity equal to?
[1 mark]
AThe beam's original weight before lifting began
BZero, because the beam moves at a steady speed
CThe beam's kinetic energy only
DThe increase in the beam's gravitational potential energy
(c)
Calculate the increase in gravitational potential energy of the 250 kg beam as it is raised 12 m, using ΔGPE = m × g × Δh with g = 10 N/kg, and then calculate the useful power output of the crane's motor during the 20 s lift, using P = E/t.
[2 marks]
Total for question 2: 4 marks
3
An electric kettle is rated to transfer 2200 J of electrical energy to its heating element every second. In one particular use, the kettle is switched on for 90 s, during which a total of 180 000 J of electrical energy is supplied to it, but only 153 000 J of this energy usefully heats the water inside; the rest is wasted, mostly as heat lost from the kettle's outer casing to the surrounding air.
(a)
Calculate the efficiency of the kettle during this use, using efficiency = useful energy transferred ÷ total energy supplied, giving your answer as a percentage.
[3 marks]
(b)
State two practical ways the manufacturer could reduce the amount of energy wasted by the kettle, and explain briefly why each change would improve efficiency.
[4 marks]
Total for question 3: 7 marks
4
A shopping centre installs a new escalator to carry customers between floors. The escalator raises a typical customer of mass 70 kg through a vertical height of 5 m as they travel up it. The escalator's motor is rated with a certain maximum useful power output, and its manufacturer publishes an efficiency figure describing what fraction of the electrical energy supplied to the motor is usefully transferred into raising customers, with the rest wasted mainly as heat in the motor and friction in the moving parts.
(a)
Explain, using the ideas of work done and gravitational potential energy, how the escalator's motor transfers energy to a customer as they are carried upward, and explain why, for the same customer, a shorter escalator carrying them through a smaller height gain would require less useful energy from the motor.
[6 marks]
(b)
The escalator's motor is not perfectly efficient. Explain, in terms of efficiency and wasted energy, what this means for the total electrical energy the shopping centre must supply to the motor compared with the useful energy delivered to customers, and describe what eventually happens to the energy that is wasted.
[6 marks]
Total for question 4: 12 marks
5
A delivery cyclist tows a small loaded trailer behind her bicycle along a flat, straight cycle path for a distance of 400 m, pulling the trailer with a constant horizontal force of 25 N acting in the same direction as the trailer's motion the whole time.
(a)
For work to be done by the cyclist's pulling force on the trailer, what condition must be met?
[1 mark]
AThe trailer must move some distance in the direction of the applied force
BThe force must be applied for exactly one second
CThe trailer's mass must be greater than 25 kg
DThe trailer must be lifted vertically off the ground
(b)
If the cyclist's pulling force were instead applied at an angle so that part of the force acted sideways, with no sideways movement of the trailer, what would happen to the work done by that sideways component of the force?
[1 mark]
AIt would do exactly the same work as the forward component
BIt would do no work, because there is no movement in the direction of that force component
CIt would double the total work done by the forward force
DIt would make the total work done negative
(c)
Calculate the work done by the cyclist's 25 N pulling force in towing the trailer 400 m, showing your working and stating the correct unit.
[2 marks]
Total for question 5: 4 marks
6
A window cleaner uses a rope-and-pulley system to raise a bucket of equipment, of total mass 15 kg, vertically up the side of a building through a height of 24 m at a steady speed. The whole lift takes 40 s to complete. Assume the gravitational field strength is g = 10 N/kg.
(a)
As the bucket is raised at a steady speed, which type of energy store increases?
[1 mark]
AKinetic energy store, which increases continuously
BChemical energy store of the rope
CGravitational potential energy store
DNuclear energy store of the bucket
(b)
Which equation should be used to calculate the useful power output needed to raise the bucket, once the work done (or energy transferred) and the time taken are known?
[1 mark]
APower = energy transferred × time taken
BPower = mass ÷ time taken
CPower = height risen ÷ time taken
DPower = energy transferred ÷ time taken
(c)
Calculate the increase in gravitational potential energy of the 15 kg bucket as it is raised 24 m, using ΔGPE = m × g × Δh with g = 10 N/kg, and then calculate the useful power needed to raise it in 40 s, using P = E/t.
[2 marks]
Total for question 6: 4 marks
7
An electric power drill is tested by an engineer. Over one minute of continuous use, the drill's motor is supplied with 54 000 J of electrical energy in total, but only 37 800 J of this is usefully transferred to turning the drill bit and cutting into the material; the remainder is wasted, mostly as heat generated by friction in the motor's bearings and gears, and as sound.
(a)
Calculate the efficiency of the drill during this test, using efficiency = useful energy transferred ÷ total energy supplied, giving your answer as a percentage.
[3 marks]
(b)
State two practical ways the engineer could improve the efficiency of the drill, and explain briefly why each change would reduce the amount of wasted energy.
[4 marks]
Total for question 7: 7 marks
8
An off-grid farm uses a solar-powered electric pump to raise water from a well up to a storage tank on a tower. The pump raises water of total mass 500 kg through a vertical height of 8 m every minute it runs. The solar panels supply the pump with a fixed amount of electrical energy each minute, but the pump itself is not perfectly efficient, and the farmer wants to understand where the supplied energy goes.
(a)
Explain, using the concepts of work done and energy transfer, how electrical energy supplied to the pump ends up raising the gravitational potential energy of the water, and calculate the useful energy transferred to the water's gravitational potential energy store each minute, using ΔGPE = m × g × Δh with g = 10 N/kg, m = 500 kg and Δh = 8 m.
[6 marks]
(b)
The solar panels actually supply the pump with 50 000 J of electrical energy each minute it runs. Using your answer to the previous part, calculate the efficiency of the pump as a percentage, and explain what is likely to be happening to the energy that is not usefully transferred to the water's gravitational potential energy store.
[6 marks]
Total for question 8: 12 marks

End of questions