Two small spheres P and Q have masses 0.1kg and 0.2kg respectively. The spheres are moving directly towards each other on a horizontal plane and collide. Immediately before the collision P has a speed of 4ms^-1 and Q has a speed of 3ms^-1. Immediately after the collision the spheres move away from each other, P with speed ums^-1 and Q with speed (3.5-u)ms^-1.

1)Find the value of u.

2)After the collision the spheres both move with deceleration of magnitude 5ms^-" until they come to rest on the plane.

Find the distance PQ when both P and Q are at rest.