Question

A 13,200 kg. railroad car is traveling at 2.1 m/s when it strikes another 12,950 kg.railroad car that is at rest. If the cars lock together, what is the final speed of the two railroad cars?( answer in m/s round to 2 sig. figs)

Answer 1

I got `1.1m/s`

Explanation:

This is a perfectly inelastic collision and we can use conservation of momentum.
Basically, the monentum before must be the same as the momentum after the impact (momentum being the product of mass times velocity).

I our case we have:

`13,200*2.1+12,950*0=(13,200+12,950)V`

where `V` will be the final valocity of the combined structure.
Rearranging to evaluate `V`:

`V=(13,200*2.1)/(13,200+12,950)=1.060038241=1.1m/s`