TPR Physics Chapter 3 FSQ #4

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today15

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I realize some has already posted a thread about this question, however I'm still having trouble getting the answer algebraically and it's really getting on my nerves :/.

Question: A box of mass m is sitting on an incline of 45 degrees and it requires an applied force F up the incline to get the box to begin to move what is the maximum coefficient of static friction?

a) [sqrt2*F / mg] - 1
b) [sqrt2*F / mg]
c) [sqrt2*F / mg] + 1
d) [2F / mg] - 1


I can get up to all this:

Since the force of friction as well as force of gravity is opposing the movement:

F = mgSin 45 + (mu) mg Cos 45

F = mg/sqrt2 + (mu)mg/sqrt2

mu = (F - mg/sqrt2) * sqrt2/mg

From this point I cannot seem to get the answer (a)...my algebra is not so great so if you could break it down that would be fantastic! Thank you!
 
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