An application of the law of conservation of linear momentum, in the horizontal direction, will tell you the answer.
Give it a try.
Adding a load by dropping from above will not change the horizontal momentum.
A 12100 kg railroad car travels alone on a level frictionless track with a constant speed of 20.5 m/s. A 5850 kg load, initially at rest, is dropped onto the car. What will be the car's new speed?
3 answers
12100kg-5850kg=6250kg/100
1/2kv2
1/2(625)(20.5)^2=
131328.125m/s
1/2kv2
1/2(625)(20.5)^2=
131328.125m/s
umm, im sorry about that answer, but really? 131 thousand meters per second? might want to check your math there, that's 131 kilometers per second which is pretty fast...