1 A small smooth sphere \(P\) of mass \(2 m\) is at rest on a smooth horizontal surface. A horizontal impulse of magnitude \(8 m u\) is given to \(P\). Subsequently \(P\) collides directly with a fixed smooth vertical barrier at right angles to \(P\) 's direction of motion. Given that the coefficient of restitution between \(P\) and the barrier is 0.75 , find the speed of \(P\) after the collision.