Question

The track shown in figure (9-E16) is frictionless. The 59. Then block B of mass 2m is lying at rest and the block A of  mass m is pushed along the track with some speed. The collision between the blocks is perfectly elastic. With what velocity should the block A be started to get the sleeping man awakened ?

Answer 1

When the block B reached at the upper man’s head, the velocity of B is just zero. For B block

Since it is an elastic collision the momentum and K.E. should be coserved.

So the block will travel with a velocity greater than 2.5 √2gh so awake the man by B