2. A particle \(P\) of mass \(3 m\) is moving with speed \(2 u\) in a straight line on a smooth horizontal plane. The particle \(P\) collides directly with a particle \(Q\) of mass \(4 m\) moving on the plane with speed \(u\) in the opposite direction to \(P\). The coefficient of restitution between \(P\) and \(Q\) is \(e\).
- Find the speed of \(Q\) immediately after the collision.
Given that the direction of motion of \(P\) is reversed by the collision,
- find the range of possible values of \(e\).