A small ball of charge Q and mass m has a velocity v at infinity. It collides head-on with a ball of the same charge and mass which is initially at rest. What is the minimal distance between the charges during the collision?

Question

Physics

Mahoney

14 June, 20:28

A small ball of charge Q and mass m has a velocity v at infinity. It collides head-on with a ball of the same charge and mass which is initially at rest. What is the minimal distance between the charges during the collision?

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Answers (1)

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Clay Barr · Answer 1

Kinetic energy of ball in motion = 1/2 m v². Potential energy = 0

Let the minimum distance between the balls be d on collision.

Electric potential energy at that time = k Q²/d, Here kinetic energy is converted into potential energy. So

1/2 m v² = kQ²/d

d = 2 k Q² / mv², = 18 x 10⁹ x Q² / m v².