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# Coefficient of friction question Watch

1. There's several parts to this question which I have been able to complete successfully , however I am having difficulties with the following ;

e. Show , further , that equilibrium is only possible when ?>?c , where

?c = ((40/81) - (4/3)*sin alpha +sin^2 alpha)/(-1/3 +cos&)

The hint is that the magnitude of F (which we know) = m?c * N . I cant' seem to form the ?c equation using this hint .

magnitude of f = ((40/81) - (4/3)*sin alpha +sin^2 alpha)
N=mg(-1/3 +cos alpha)

Note the ? are supposed to represent the symbol for the coefficient of static friction .
Thank you for your help .

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Updated: November 30, 2010
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