- Two particles \(P\) and \(Q\) have masses \(4 m\) and \(m\) respectively. They are moving in opposite directions towards each other along the same straight line on a smooth horizontal plane and collide directly. Immediately before the collision the speed of \(P\) is \(2 u\) and the speed of \(Q\) is \(4 u\). In the collision, the particles join together to form a single particle.
Find, in terms of \(m\) and \(u\), the magnitude of the impulse exerted by \(P\) on \(Q\) in the collision.