(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

See the diagram here: http://i47.photobucket.com/albums/f173/xallip/bar2-1.jpg

Known quantities: L, F_{f}.

a) Find the x and y components of A and B.

b) μ is a known quantity; give an expression for A in this case.

2. Relevant equations

3. The attempt at a solution

a) Rx = Ff

N + Ry - mg = 0

net torque about the blue point must also be zero.

I'm unsure how to calculate the torque, since the entire length of the plank isn't spanned by the step and floor. Does gravity still act at the center of mass, 0.5L? If so then net torque:

0 = 0.9LR - mg0.5Lcosθ

Then I can solve for R: R = (mg0.5Lcosθ)/0.9L = (5/9)mgcosθ

And knowing R and Rx I can get Ry (pythagoras' thm), and from Ry I can find N. Is that correct?

b) This is what's really confusing me! I thought Ff = μN so N = Ff/μ, but I don't think it can be that simple.

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# Forces Free Body Diagram & Finding μ

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