AS June 2025 Q1

1. A car of mass 1000 kg moves along a straight horizontal road at a constant speed \(U\ \text{m s}^{-1}\). The engine of the car is working at a rate of 20 kW.

The total resistance to the motion of the car is modelled as a constant force of magnitude 1600 N.

Using the model,

Later on, the car moves down a straight road which is inclined to the horizontal at an angle \(\alpha\), where \(\sin\alpha = \dfrac{1}{49}\)

The total resistance to the motion of the car is again modelled as a constant force of magnitude 1600 N.

At the instant when the engine of the car is working at a rate of 20 kW and the speed of the car is \(8\ \text{m s}^{-1}\), the acceleration of the car is \(a\ \text{m s}^{-2}\)

Using the model,