A set of n identical cubical blocks lies at rest parallel to each other along a line on a smooth horizontal surface. The separation between the near surfaces of any two adjacent blocks is L. The block at one end is given a speed v towards the next one at time t=0 . All collisions are completely inelastic, then
(a) The last block starts moving at t=(n-1)L/v
(b) The last block starts moving at t=n(n-1)L/2v
(c) The centre of mass of the system will have a final speed v
(d) The centre of mass of the system will have a final speed v/n
Answer: b
(8)