Short answerEasy1 mark
6(iii)
A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate:
the power of the engine.
Topic: Power
Question wording verified against source paper
Answer
Exam answer
Given: work done W = 12 000 J (from part (a)), time t = 5 s
Power = work done ÷ time taken = 12 000 ÷ 5 = 2 400 W
Power of the engine = 2 400 W (2.4 kW)
Explanation
Now the 5 seconds earns its place. Power is simply the rate of doing work, so divide the energy by the time.
Multiplying instead gives 60 000, and the units alone should catch it: joules divided by seconds gives watts, joules times seconds gives nothing useful. Writing the units beside each number as you substitute is the cheapest error check there is.
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