When a light body collides against a massive body at rest, the light body rebounds after the collision with an equal and opposite velocity while the massive body practically remains at rest. A light ball striking a wall rebounds almost with the same speed and the wall remains at rest.

When a massive body collides against a light body at rest, the velocity of the massive body remains almost unchanged while the light body starts moving with a velocity wise the velocity of the massive body.

 If a force acts perpendicular to the direction of a body, the amount of work done is zero because there is no displacement in the direction of a force.