(a)[3]
Determine the values of $m$ and $u$.
(b)[4]
Particle $P$ is projected on a smooth horizontal surface with speed $v\,\text{m s}^{-1}$ directly towards a stationary particle $Q$ of mass $1.25\,\text{kg}$. After the collision between $P$ and $Q$, the velocity of $P$ is $w\,\text{m s}^{-1}$ and the velocity of $Q$ is $2w\,\text{m s}^{-1}$. The decrease in kinetic energy during the collision is $25\,\text{J}$. Find the values of $v$ and $w$.