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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.