Energy, work and power — practice question

Particle $P$ is launched from the upper end of a smooth ramp with speed $u\,\text{m s}^{-1}$ and moves along the steepest descent. The ramp is $6.4\,\text{m}$ long and makes an angle of $30^\circ$ to the horizontal. At the same moment that $P$ is launched, a second particle $Q$ is let go from rest at a point $3.2\,\text{m}$ vertically above the foot of the ramp (see diagram). If $P$ and $Q$ arrive at the bottom of the ramp at the same time,