A-level · Work, energy & power

PowerExam-style questions

Power as the rate of doing work, average power = work ÷ time, and the key working relationship P = Fv for a driving force — used to find engine power at constant speed and, by combining P = Fv with Newton's second law, the instantaneous acceleration of a vehicle on a level road or a hill.

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22 questions · A Level level · mark scheme and worked solution on each · no sign-up to try

DifficultyAll Level 1 Level 2 Level 3 Level 4 Level 5

1
A crane does $60000\text{ J}$ of work in raising a load in $20\text{ s}$ . Find the average power developed. (2 marks)
Level 1 · 2 marksTry it
2
A motor does $5400\text{ J}$ of work in $30\text{ s}$ .

Find its average power. (2 marks)
Level 1 · 2 marksTry it
3
A car moves along a straight road at a constant speed of $25\text{ m s}^{-1}$ . Its engine works at a rate of $20000\text{ W}$ . Find the driving force produced by the engine. (2 marks)
Level 2 · 2 marksTry it
4
A car travels along a level road at a constant speed of $25\text{ m s}^{-1}$ against a total resistance of $600\text{ N}$ .

Find the power developed by the engine. (3 marks)
Level 2 · 3 marksTry it
5
A cyclist works at a constant rate of $250\text{ W}$ and moves at a constant speed of $5\text{ m s}^{-1}$ on level ground.
(a) Find the driving force the cyclist produces. (2 marks)
(b) Write down the total resistance to the cyclist's motion. (1 mark)
Level 2 · 3 marksTry it

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