## joshi 3 years ago 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 25,000 N 20,000 N 15,000 N 10,000 N

1. ivanmlerner

This tension must be enough to pull both cars behind the engine car, but not the engine car, at an aceleration of 5m/s^2. Remember that F=ma

2. joshi

@ivanmlerner still pretty confused. i've calculated the total force and the seperate forces as well but i'm not getting the correct answer.

3. ivanmlerner

No, you dont consider the engine car, because the tension is pulling only the last two. Probably thats what your getting wrong.

4. ivanmlerner

Ok, the mass is 3000, because you dont consider the engine car, then 3000*5=F=15000N

5. ksaimouli

why should we not consider that

6. ivanmlerner

|dw:1350081459057:dw| The last car needs to have the same acelerationa s the others, so you need less force to pull it, the second car needs to pull the last and be pulled, so it is the force for pulling the last plus the force of pulling the second, and so on

7. joshi

ohhhh i think i get it now. thanks!