Mathematics 9709 · AS & A Level · Energy, work and power
Energy, work and power — practice question
A car with mass $600\,\text{kg}$ is moving on a straight horizontal road, having set off from point $A$. The force resisting its motion is $750\,\text{N}$.
(i)[3]
In $100\,\text{s}$, the car moves from $A$ to $B$ at a steady speed. The engine delivers constant power of $30\,\text{kW}$. Determine $AB$.
(ii)[3]
At $B$, the engine is turned off and the car slows down until it arrives at $C$ with speed $20\,\text{m s}^{-1}$. Find $BC$.
(iii)[4]
At $C$, the engine is switched on and supplies constant power of $30\,\text{kW}$. The car takes $14\,\text{s}$ to move from $C$ to $D$ and arrives at $D$ with speed $30\,\text{m s}^{-1}$. Find $CD$.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “From $DF=30000/v$ or by taking work done by driving force $=30000\times100$” …