Question

An improvised billiard ball is used in a local play where a 35 gram billiard ball resting in a corner is suddenly

hit by another 45 grams ball moving 0.5 m/s. After the collision, the 45 grams ball remains at rest while the

other ball moves away. Find the velocity of the ball moving away ?

Answer 1

Given:

$v_1=0$

$m_1=35\:\rm g$

$v_2=0.5\:\rm m/s$

$m_2=45\:\rm g$

$v_2'=0$

The law of conservation of momentum says

$$m_1v_1+m_2v_2=m_1v_1'+m_2v_2'$$

Thus

$$v_1'=v_1+(v_2-v_2')m_2/m_1$$

$$v_1'=0+(0.5-0)45/35=0.64\:\rm m/s$$