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Question
In a head-on collision between two particles, is it necessary that the particles will acquire a common velocity at least for one instant?
Solution
Yes.
For example, consider particle-1 at a velocity of 4 ms-1 and particle-2 at a velocity of 2 ms-1 undergo a head-on collision.
The velocity of particle-1 decreases but particle-2 increases. Therefore, at an instant, their velocities will be equal.
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