Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Linear Momentum of the Ball


To get a feeling of linear momentum.


two plastic balls


Take two identical plastic balls. Make a hole in one of them and fill it with sand. Seal the hole with tape. Now you have two balls of different masses. Make a pile of sand on the floor and drop the lighter ball on it from a height. The ball will penetrate into the sand to some depth. Make the pile again and drop the heavier ball on it from the same height. This ball will penetrate deeper into the sand. Dropping from the same height ensures that balls strike the sand with the same velocity. So, increasing the mass increases the depth of penetration when the velocity remains the same.


Now drop one of the balls from different heights on the pile. Dropping from a larger height means the ball strikes the pile with larger velocity. So, increasing the velocity increases the depth of penetration when the mass remains the same.

If you drop the lighter ball from a greater height and the heavier ball from a lower height, it may happen that the depths of penetration become the same. This will happen when the product \(mv\) is the same.