Mathematics 9709 · AS & A Level · Energy, work and power
Energy, work and power — practice question
A car with mass $1200\,\text{kg}$ is moving along a straight horizontal road. The car’s engine has constant power equal to $16\,\text{kW}$. A constant resistive force of magnitude $500\,\text{N}$ acts on the car.
(a)[3]
Find the car’s acceleration at the moment when its speed is $20\,\text{m s}^{-1}$.
(b)[2]
Find the steady speed at which the car can travel, assuming that the power and the resistance forces remain unchanged.
(c)[6]
Given that the car is moving at $20\,\text{m s}^{-1}$ at the foot of the hill, determine its speed at the summit.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct value for driving force $F=\tfrac{16000}{20}=800$.” …