A ball of mass 0.50 kg moving at a speed of 5.0 m/s collides with another ball of mass 1.0 kg. After the collision the balls stick together and remain motionless. What was the velocity of the 1.0 kg block before the collision?

Question

Philoid · Accepted Answer

Let the velocity of the other ball before collision, be ‘v’ m/s

Initial momentum of the ball before collision = 0.50×5

= 2.5 kg m/s

Initial momentum of the other ball before collision = 1.0×v

= v kg m/s

Total initial momentum of the two balls = (2.5+v) kg m/s

After collision, both the balls stick together and come to rest.

Final momentum of the two balls after collision = 0 kg m/s

Applying conservation of total linear momentum

⇒ 2.5 + v = 0

⇒ v = –2.5 m/s

∴ The velocity of the ball before collision was 2.5 m/s opposite to the direction of motion of the first ball.