Try this problem, useful for Physics Olympiad based on Collision Between Two Balls.

**The Problem: **

A ball A moving with a velocity 5m/s collides elastically with another identical ball at rest such that the velocity of the A makes an angle of \(30^\circ\) with the line joining the centres of the balls. Then,

(A) speed of A after collision is \(\frac{5}{2}m/s\)

(B) speed of B after collision is \((5\sqrt{3}/2)\)m/s

(C) balls A and B move at right angles after collision

(D) Kinetic energy is not conserved as the collision is not head-on

**Solution:**

Since the angle is \(30^\circ\), the speed of A after collision will be \(\frac{5}{2}m/s\)

The speed of B after collision will be \((5\sqrt{3}/2)\)m/s since the speed will be \(5cos30^\circ\)

The balls A and B move at right angles after collision.

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