Two bodies of mass 4 kg and 6 kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless. The acceleration of the system in terms of acceleration due to gravity (g) is :

  (a) g           (b) g/2           (c) g/5           (d) g/10

A ball is moving with a velocity 2 m/s collide head on with another stationary ball of double mass if the coefficient of restitution is 0.5 then their velocities, (m/s ) After collision will be

[CBSE-PMT-2010]  (a) 0 , 1         (b) 1 , 1      (c) 1 , 0.5      (d) 0 , 2