The resistance to motion of a car due to air resistance is proportional to the square
of its speed. The car has a mass of 1000 kg and can maintain a steady speed of 30
ms−1 when travelling up a hill inclined at 2.37◦ to the horizontal with the engine
working at 60 kW.
Find the acceleration of the car when it is travelling down the same hill with the engine working at 40 kW at the moment when the speed is 20 ms−1.