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## Homework Statement

An object of mass M=10kg is being pulled up by a system of pulleys.

a)What force do you need to exert on point A for the object to move uniformly ?

b) What force do you need to exert on point A, if the friction in each of the pullies is 0,5N and the pulleys are not massless - the mass of the 1st one is 100g, the 2nd - 200g, the 3rd - 300g, the 4th- 400g.

http://img148.imageshack.us/img148/5526/unledbde.jpg [Broken]

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## Homework Equations

## The Attempt at a Solution

I solved the A part quite easily, got a result of F=12,5N, but i'm stuck with part B - i can't figure out the directions of the friction forces .

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