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A 68 kg crate is dragged across a floor by pulling on a rope attached to the crate and inclined 158 above the horizontal. (a) If the coefficient of static friction is 0.50, what minimum force magnitude is required from the rope to start the crate moving?

The book suggests this: https://i.stack.imgur.com/x6xHn.png

I don't understand where the ps (sinangle) comes from.

I have Tension = Ps X mg / cos angle. But where does sin angle come from?

user416503
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  • Can you upload a figure of the problem? – jonsno Mar 06 '17 at 10:54
  • theres no figure – user416503 Mar 06 '17 at 11:06
  • This might be more appropriate for http://physics.stackexchange.com/. – amd Mar 06 '17 at 20:31
  • Strange you don't have a figure of the problem. See here https://www.physics.ohio-state.edu/~gan/teaching/spring99/C6.pdf for deduction of the formula. You will find a minus in it because the force is pointing downwards. So in your case the force is pointing upwards. – cgiovanardi Mar 07 '17 at 04:35

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