Mathematics 9709 · AS & A Level · Energy, work and power
Energy, work and power — practice question
A car with mass $1400\text{ kg}$ is moving along a straight horizontal road and accelerates uniformly from $15\text{ m s}^{-1}$ to $20\text{ m s}^{-1}$ across a distance of $175\text{ m}$. A constant resistive force of $800\text{ N}$ acts opposite to the car’s motion.
(a)[2]
Find the time taken to cover the $175\text{ m}$.
(b(i))[4]
Use an energy method throughout to determine the average power of the car’s engine while the speed rises from $15\text{ m s}^{-1}$ to $20\text{ m s}^{-1}$.
(b(ii))[2]
Find the steady speed that the car could maintain on the horizontal road if the engine is operating at the power found in (b)(i).
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Set up an equation in time by using area/kinematics” …