(i)[2]
Calculate the power needed to keep a constant speed of $30\ \text{m s}^{-1}$.
(ii)[5]
The lorry reaches a straight hill that is inclined at $2^\circ$ to the horizontal. The driver switches off the lorry’s engine at point $A$, which is at the bottom of the hill. Point $B$ is further along the hill. The speeds of the lorry at $A$ and $B$ are $30\ \text{m s}^{-1}$ and $25\ \text{m s}^{-1}$ respectively. The resistance force is still $3000\ \text{N}$. Use an energy method to determine the height of $B$ above the level of $A$.