Question

A 20000kg railroad car is traveling at 5 m/s when it collided and coupled with a second, identical car at rest. What is the resulting speed of the combined cans?

Answer 1

We know that in a collision the momentum of the system is conserved, that is:

`p_i=p_f`

In this case, since the railroad cars coupled together and have the same mass we have:

`mv_1+mu_1=2mv`

Now, we know the initial velocity of the cars, one is traveling at 5 m/s and the other is at rest; plugging the values and solving for the final velocity we have:

`\begin{gathered} 20000(5)+20000(0)=2(20000)v \\ v=(5(20000))/(2(20000)) \\ v=2.5 \end{gathered}`

Therefore, the velocity of the combined cars is 2.5 m/s