Question

Three identical train cars, coupled together, are rolling east at speed v0. A fourth car traveling east at 2v0 catches up with the three and couples to make a four-car train. A moment later, the train cars hit a fifth car that was at rest on the tracks, and it couples to make a five-car train.

What is the speed of the five-car train?

Express your answer in terms of v0

Answer 1

`1v_0`

Step-by-step explanation:

Assuming that cars 4 and 5 have same mass so that the momentum

P=mv where m is mass and v is velocity hence

Momentum=0+2mv+3mv=5mv

The final mass is 2m+3m=5m

From aw of conservation of momentum

`5mv_0=5mv` hence
`v=1v_o`

Therefore, the speed is
`1v_0`