Probability — practice question

A particle $P$ with mass $0.4\text{ kg}$ is released from rest at point $O$ on a smooth plane inclined at $30^{\circ}$ to the horizontal. If the displacement of $P$ from $O$ is $x\text{ m}$ down the plane, its velocity is $v\text{ m s}^{-1}$. A force of magnitude $0.8\mathrm{e}^{-x}\text{ N}$ acts on $P$ up the plane along the line of greatest slope through $O$.