Answered

At Westonci.ca, we provide clear, reliable answers to all your questions. Join our vibrant community and get the solutions you need. Connect with a community of professionals ready to provide precise solutions to your questions quickly and accurately. Join our platform to connect with experts ready to provide precise answers to your questions in different areas.

Can someone explain why the answer is this?
The question is the following:
A large locomotive with a mass 4 times that of the smaller motionless railroad car collides and couples together. What is their combines speed after the collision?

I saw my classmates working out and she said its this but I don't understand WHY its like this and not any other way:

4m x 5 + m x o = 4mv + mv
20m + 0.5mv
20m = 5mv
v = 20m/5m
v = 4km/h