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Question
What is inelastic collision? In which way it is different from an elastic collision. Mention a few examples in day-to-day life for inelastic collision.
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Solution
Inelastic collision: In a collision, the total initial kinetic energy of the bodies (before the collision) is not equal to the total final kinetic energy of the bodies (after collision) then, it is called as inelastic collision, i.e.,
Total kinetic energy before collision ≠ Total kinetic energy after collision
`("Total kinetic energy after collision") - ("Total kinetic energy before collision") = ("loss in energy during collision") = DeltaQ`
Even though kinetic energy is not conserved but the total energy is conserved. This is because the total energy contains the kinetic energy term and also a term ∆Q, which includes all the losses that take place during a collision. Note that loss in kinetic energy during collision is transformed to another form of energy like sound, thermal, etc. Further, if the two colliding bodies stick together after collision such collisions are known as completely inelastic collision or perfectly inelastic collision. Such a collision is found very often. For example when a clay putty is thrown on a moving vehicle, the clay putty (or Bubblegum) sticks to the moving vehicle and they move together with the same velocity.
Difference between Elastic & inelastic collision
| S.No. | Elastic | Inelastic |
| 1. | Total kinetic energy is conserved. | Total kinetic energy is not conserved. |
| 2. | The forces involved are conservative forces. | The forces involved are non-conservative forces. |
| 3. | Mechanical energy is not dissipated. | Mechanical energy is dissipated into heat, light, sound, etc. |
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