Physics Concepts for JEE – Cases of Mass Variation and Super Elastic Collision
There are many cases in which the mass of a body changes. It may increase or decrease while the body is in motion. Such cases are explained with the concept of Mass Variation. When a body is moving and its mass is changing, the momentum of body changes due to two reasons –
(1)
The presence of some external
force acting on the body.
(2)
The change in mass which may
add or extract momentum to or from the body.
To analyze such cases, we can write the equation
for momentum conservation or Impulse momentum at an intermediate time t and
t+dt. Then, integrate it for the required parameter of motion for the given
duration of motion.
To understand how to apply the concept and
how to handle such cases of mass variations, see the video below which includes
the concept analysis and solved examples for explanation –
Super Elastic Collisions: When the Coefficient
of Restitution in a given collision is more than one (e>1), the kinetic
energy of system after collision is more than that of the initial kinetic
energy of the system. In such cases, at the moment of collision some energy is
evolved. See the video below for explanation –