Use \(g=10\text{ m s}^{-2}\).

A 4 kg block is pulled along a rough horizontal road by a constant 25 N force at \(36^\circ\) above the horizontal. It moves in a straight line from \(A\) to \(B\), with \(AB=120\text{ m}\). The coefficient of friction is 0.4.

(a) Find the work done against friction from \(A\) to \(B\). [3]

The speed at \(A\) is \(7\text{ m s}^{-1}\).

(b) Use an energy method to find the speed at \(B\). [4]