A35-gram stainless steel ball on a track is moving at a velocity of 9 m/s. on the same track, a 75-gram stainless steel ball is moving at a velocity of –7 m/s. after colliding, the 35-gram ball moves at a velocity of –15 m/s. assume there is no net force on the system. what is the velocity of the 75-gram ball after the collision? round to the nearest tenth. –4.2 m/s –0.5 m/s 0.5 m/s 4.2 m/s

  Option D is the correct answer.

Explanation:

 The given figure shows the arrangement

  We have momentum is conserved before and after collision.

  Momentum before collision

                                     = 35 * 9 + 75* (-7) =   -210 g m/s

 Momentum after collision

                                    = 35 * (-15) + 75 * V = 75 V - 525

            V is the velocity of 75 g ball after collision.

  We have momentum conservation equation

          So,    -210 = 75 V - 525

                     75 V = 525 - 210 = 315

                          V = 4.2 m/s

  So velocity of 75 g ball is 4.2 m/s.

  Option D is the correct answer.