At 5000-kg freight car runs into 10000-kg freight car at rest. they couple upon collision and move with a speed of 2 m/s. what was the initial speed of the 5000-kg car?

Solution for the problem is:

Total momentum before collision is always equal to total momentum after collision. So note that:

Momentum of car A = 5000 x Xm/s

Momentum of car A + B = 15,000 x 2m/s

So combining the two, will give us the equation:

15,000/5,000 = 3

3 x 2 = 6m/s