Question

In a closed system, an object with a mass of 10 kg moves at a velocity of 5.4 m/s. It collides with a second object that has a mass of 12 kg and that is moving in the opposite direction with a velocity of 3.5 m/s. What is the total momentum of the system after the collision?

Answer 1

Momentum is conserved in a closed system, so total momentum after the collision equals the total momentum before it.

Take the direction of the 10 kg object as positive. Then the 12 kg object's velocity is negative:

p = m1 v1 + m2 v2 = 10(5.4) + 12(−3.5) = 54 − 42 = 12 kg·m/s.

So the total momentum after the collision is 12 kg·m/s in the direction the 10 kg object was originally moving.