# B Momentum in a complicated system

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1. Aug 21, 2016

### ddddd28

let's assume we have a wagon in a wagon in a wagon and so on, which can move freely. friction is negligible. their mass is same. what will happen if someone gives a push to the whole system?

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2. Aug 21, 2016

### BvU

Hello 5d,

If the push is from the outside, only the outer wagon will accelerate.

3. Aug 21, 2016

### A.T.

Initially.

4. Aug 21, 2016

### ddddd28

but what happens after the collision of the inner wagon ?

5. Aug 21, 2016

### A.T.

Elastic or inelastic?

6. Aug 21, 2016

### ddddd28

elastic. all the conditions are ideal.

7. Aug 21, 2016

### BvU

Is this a real exercise or a figment of the imagination ?
When the first inner wagon hits the back wall of the outer one, there is a collision, apparently with kinetic energy conservation. But definitely with momentum conservation. Without any givens at all, there isn't much to say about this. Inner wagons will bounce back and forth, so the outer wagon will move irregularly.

8. Aug 21, 2016

### ddddd28

This is not a real problem. being interested to build that system, since it probably will not perform a "regular motion", but failed to predict it. let's assume each wagon is half of the length of the outer one , and there are four of them, for simplicity. how exactly the outer wagon will move?

9. Aug 21, 2016

### BvU

You forgot to give several needed given data, including the initial conditions for these equations