A railroad car of 2000 kg coasting at 3.0 m/s overtakes and locks with an identical car coasting on the same track in the same direction at 2.0 m/s. What is the speed of the cars after they lock together?

Question

Physics

Sonny Cannon

11 June, 10:48

A railroad car of 2000 kg coasting at 3.0 m/s overtakes and locks with an identical car coasting on the same track in the same direction at 2.0 m/s. What is the speed of the cars after they lock together?

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Answers (1)

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Sean Blanchard · Answer 1

The key is in "they lock together". This tells you this is a complete inelastic collision and therefore you can use the formula:

m1*v1+m2*v2=v (m1+m2)

Plug in numbers:

2000*3+2000*2=v (2000+2000)

so v=2 m/s, obviously in the same direction of motion in which they were both moving.