1. Dec 2, 2009

### slobodan48

how do you find the Tension force,acceleration,magnitude.
Its those questions where you have pullys,boxes pushing each other...
I am really confused for the 3rd law

2. Dec 2, 2009

### Cryxic

Do you have a specific example? I'd hate to just vapidly repeat the definition of the 3rd law, which you can easily find anywhere and everywhere....

3. Dec 2, 2009

### slobodan48

Two masses are places in a frictionless pulley system.Solve for the acceleration and tension forces.
1st box is 4kg and the other is 3kg

well i know,
fnet=ma
fg=mg
ff=muFn

4. Dec 3, 2009

### sophiecentaur

You could start by saying that there is a net, unbalanced force of 10N (For GCSE level thought - or you can do 9.81m/s/s, if you like), pulling one up and one down.
This is accelerating both the masses (7kg total), use your formula to find the acceleration.
The tension will be ml times (g + this acceleration) for the light mass and also mh times (g- this acceleration) for the heavy mass. Those two values should be the same, natch - as a check.
etc etc - you can put in the numbers