Question

A ball moving with a velocity of 9 m/sec collides with another similar stationary ball. After the collision both the balls move in directions making an angle of 30° with the initial direction. After the collision, their speed will be:-

Answer 1

Conservation of linear momentum in the direction perpendicular to the initial velocity :
$m{v}_{1}sin{30}^0-m{v}_{2}sin{30}^0=0$

$v_1=v_2$

Conservation of linear momentum in the direction of initial velocity of the first ball:
$mu=m{v}_{1}cos{30}^0-m{v}_{2}cos{30}^0$

9 = 2 v cos 30 = √3 v

v = 3√3 m/s = 5.2 m/s

After collision, the speed of both balls will be approximately 5.2 m/s.