Mathematics 9709 · AS & A Level · Energy, work and power

Energy, work and power — practice question

A car with mass $1200\,\text{kg}$ is travelling along a straight road while a steady resisting force of $850\,\text{N}$ acts against its motion.
(i(a))[2]

On a horizontal stretch of the road, the car travels at a constant speed of $42\,\text{m s}^{-1}$. Calculate, in kW, the power developed by the engine of the car.

(i(b))[3]

If this power is increased suddenly by $6\,\text{kW}$, determine the car’s instantaneous acceleration.

(ii)[4]

On a section of road inclined at $\theta^\circ$ to the horizontal, the car climbs the hill at a constant speed of $24\,\text{m s}^{-1}$, with the engine running at $80\,\text{kW}$. Find $\theta$.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: Apply $P = Fv$ and take $P = 850 \times 42$

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