# A rocket and a box

Gold Member
This is actually not a homework but it looks like one.So I posted here

## Homework Statement

A rocket is pushing a box on empty space.
The rocket is exerting a force on the blue colored box.In turn the box is exerting the same force on the rocket.The engine(or fire or whatever) it exerting a force on the rocket..

## The Attempt at a Solution

At first the rocket gets close to the box,as it gets closer,the electromagnetic force builds up(the box starts to move) until the force from the engine and electro balance.The rocket moves at a constant velocity even closer to the box the electomagnetic force now exceeds the engine force and move at more acceleration.Again the rocket contacts and do the same.Will it keep bouncing like that if there were no energy loss?
And is my explanation right at the first place?

What would be a better explanation.I haven't studied such types of collision yet(or any types).So please be descriptive.

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tiny-tim
Homework Helper
A rocket is pushing a box on empty space.
The rocket is exerting a force on the blue colored box.In turn the box is exerting the same force on the rocket.The engine(or fire or whatever) it exerting a force on the rocket..

sorry, i don't understand what the question is asking for

Gold Member

sorry, i don't understand what the question is asking for
Just imagine that a person(Stationary) is observing a rocket driving a box across the empty space(No resistance forces.)
What Explanation could the observer give?
Is my explanation correct?

SteamKing
Staff Emeritus
Homework Helper
I doubt it. It doesn't make any sense.

If the box is not fixed "in space" in any way, it will be pushed by the rocket, with increasing velocity, till the rocket runs out of fuel. Then they will travel with some constant velocities, and the box will have a slightly greater velocity that the rocket. Why that is so is left as an exercise to the reader.

During the initial impact and shortly after, there will be oscillations in the box-rocket system. Also an exercise.

Gold Member
During the initial impact and shortly after, there will be oscillations in the box-rocket system. Also an exercise.
Yes this was what I was asking for.Sorry if it did not make any sense.
Why do you think the bouncing stops,because it(collistion)loses energy?

CWatters
Homework Helper
Gold Member
At first the rocket gets close to the box,as it gets closer,the electromagnetic force builds up(the box starts to move) until the force from the engine and electro balance.The rocket moves at a constant velocity even closer to the box the electomagnetic force now exceeds the engine force and move at more acceleration.Again the rocket contacts and do the same.Will it keep bouncing like that if there were no energy loss?
And is my explanation right at the first place?

So in short you have an accelerating object (a rocket) colliding (elastically) with another object (the box).

As long as the collision is elastic then yes it will keep bouncing off.

Not sure what happens if the combination approaches the speed of light :-)

Yes this was what I was asking for.Sorry if it did not make any sense.
Why do you think the bouncing stops,because it(collistion)loses energy?

Yes.

Gold Member
Thank you all so much