Maximum Static Friction

[colemansmith]

1. The problem statement, all variables and given/known data
Basically, I need to find the maximum static friction of my shoe against a wood board.
I discovered that after increasing the slope of the board, my shoe slipped at an angle of 29.33 degrees. (using tan theta = O/A) O being 42.7 cm and A being 76 cm. The shoe has a weight of 5 Newtons. I calculated the mass of the shoe by using the formula Fg = mg, where Fg = 5, and g = 9.8. Thus: 5 = m(9.8) which equals 0.51.
A quick recap:
theta = 29.33 degrees
weight (Fg) = 5
mass = 0.51

I am supposed to find the Maximum Static Friction of my shoe against the wood. I do not[b/] know the co-efficients of either (we are not supposed to use them from out text's)




[b]2. Relevant equations

tan theta = O/A

Fg = mg

Ff = u Fn (u is miu or the frictional co-efficient)

3. The attempt at a solution

Here is a diagram depicting my work so far.
http://i44.tinypic.com/w8nyah.jpg




I am basically stuck. Any help would be great (formulas, tips, anything)

Thanks guys and gals

Coleman.

[BishopUser]

Your diagram misses a coordinate system. Try to think of a coordinate system that would make the problem easier. Specifically, a coordinate system in which one or more of the forces acted entirely in the X or Y direction. Once you break the forces into their x/y components you can then use the equations you listed.