# Contrary movement

When 2 objects placed one on each other and one of them pulled, the second will move in a contrary way.

there is a way to proof it with newtons law ???

tnx .

tiny-tim
Homework Helper
When 2 objects placed one on each other and one of them pulled, the second will move in a contrary way.

there is a way to proof it with newtons law ???

tnx .

Hi sedaw!

I'm not sure what you mean … can you be more specific?

Do you mean that, for example, if a man is standing on a table on wheels, and he walks forward, then the table will move backward?

That's because of Newton's first law … no external forces are acting, so the centre of mass stays at the same (stationary) velocity … in other words, it stays where it is.

Alternatively, use Newton's third law … for the man to walk, there must be a force on him from the table, and so there must be an opposite force from him on the table, which makes the table move the opposite way.

Or use Newton's second law …

Or am I misunderstanding the question?

http://img516.imageshack.us/img516/754/3232ej8.jpg [Broken]

Hello !

i`m hope it will be clear now...

if the force F will work on the object A and make em move to the right side the object B will move or aspire to move to the left.

why is that ?

TNX

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tiny-tim
Homework Helper
if the force F will work on the object A and make em move to the right side the object B will move or aspire to move to the left.

No … if there is friction, B will move to the right (only very slightly, if you pull hard enough);

if there is no friction, B will remain stationary.

so the friction cause to the movment ?

tiny-tim
Homework Helper
so the friction cause to the movment ?

Yup!

The friction causes the movement.​

HallsofIvy