Question

- A 9,300 kg. railroad car traveling at a velocity of 15m/s strikes a second boxcar

at rest. If the two cars stick together and move off with a velocity of 6m/s, what is the mass
of the second car?

Answer 1

13950kg

Step-by-step explanation:

If we make the system both railroad cars, we know that the momentum of the whole system doesn't change because the forces are internal.

Let a be the mass of the second car.

The original momentum is 9300*15 kg*m/s+ a*0 kg*m/s = 139500 kg*m/s

After sticking together, the momentum is (9300+a)kg*6m/s, which should be equal to 139500 kg*m/s

Therefore (9300+a)*6 = 139500

9300+a = 23250

a = 13950 kg