A moving block having mass m, collides with another stationary block having mass 4m. The lighter block comes to rest after collision. When the initial velocity of the lighter block is v, then the value of coefficient of restitution (e) will be

A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes a vertical circle of diameter AB = D. The height h is equal to

Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m s^$$-$$1. Take 'g' constant with a value 10 m s^$$-$$2. The work done by the (i) gravitational force and the (ii) resistive force of air is

Two identical balls A and B having velocities of 0.5 m s^$$-$$1 and $$-$$0.3 m s^$$-$$1 respectively collide elastically in one dimension. The velocities of B and A after the collision respectively will be