Question

A Ball A and a Ball B collide elastically. The initial momentum of Ball A is 14.0kgm/s and the initial momentum of Ball B is -9.00kgm/s. Ball A has a mass of 2.00kg and is traveling at -5.00 m/s after the collision. What is the velocity of ball B if it has a mass of 3.00kg

Answer 1

The total momentum before collision is

14.0 kg•m/s + (-9.00 kg•m/s) = 5.00 kg•m/s

If v is the velocity of ball B after colliding with ball A, the total momentum after collision is

(2.00 kg) (-5.00 m/s) + (3.00 kg) v

Momentum is conserved, so these quantities are equal. Solve for v :

5.00 kg•m/s = (2.00 kg) (-5.0 m/s) + (3.00 kg) v

5.00 kg•m/s = -10.0 kg•m/s + (3.00 kg) v

15.0 kg•m/s = (3.00 kg) v

v = (15.0 kg•m/s) / (3.00 kg) = 5.00 m/s