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## Homework Statement

a 20kg block rests on a horizontal surface and is attatched to a mass of 3.5kg by a cable,the pulley is frictionless ans the coefficient of static frition is 0.2

prove that the mass is not suffcient to start the block moving,what is the additional mass that would be requaired to start motion

## Homework Equations

http://img818.imageshack.us/img818/9962/37642403.png [Broken]

## The Attempt at a Solution

20kg block Ff=39.24 Fn=196.2

3.5kg block Fw=34.33

i can work out the acceleration which is 6.68 m/s

but i just dont know hwo togo about working out what it is asking to do,as in prove the mass is not sufficient to start the block moving,what additonal forceis needed

any help would be great Thanks

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