Question

Simple mechanics/forces question!

A train consists of a caboose (mass = 1000 kg), a car (mass 2000 kg), and an engine car (mass 2000 kg). If the train has an acceleration of 5 m/s2, then the tension force in the coupling between the middle car and the engine car is:

A) 25,000N
B) 20,000N
C) 15,000N
D) 10,000N

I know the answer is 15,000N, but would someone mind explaining why/how?
Thanks!

(Picture is at http://cwx.prenhall.com/giancoli/chapter4/medialib/f4-7.gif )

Answer 1

because if the caboose and car are accelerating at 5 m/s^2, there must be a force acting on them equal to (1000+2000)*5
that force has to come only from the tension.

Answer 2

So we treat the Caboose and Car as a single entity, and the tension between the car and engine is equal to 3000*5?

Answer 3

yep.

Answer 4

Thanks!

Answer 5

sure!