A 90-kg halfback running north with a speed of 10 m/s is tackled by a 120-kg opponent running south at 5.0 m/s.The collision is perfectly inelastic.Compute the velocity of the two players just after the tackle.
A) 1.4 m/s south
B) 2.8 m/s south
C) 2.8 m/s north
D) 1.4 m/s north

Question

Quizplus · Accepted Answer

In a perfectly inelastic collision, momentum is conserved. The total momentum before the collision is (90 kg * 10 m/s) - (120 kg * 5 m/s) = 900 kg*m/s - 600 kg*m/s = 300 kg*m/s north. The combined mass after the collision is 90 kg + 120 kg = 210 kg. The velocity is 300 kg*m/s / 210 kg = 1.4 m/s north.

A 90-Kg Halfback Running North with a Speed of 10