Find Coefficient of Friction for Firefighter on Ladder

[boomclapslap]

Homework Statement

(8 marks)
A uniform ladder (m = 35kg) leans against a smooth frictionless wall. The foot of the ladder is 3 m from the wall and an 85kg firefighter stands 3m up the ladder as shown. Find the coefficient of friction of the floor.
http://i49.tinypic.com/ftdo9g.jpg

Homework Equations

(Angular Newton's Second Law and Linear Newton's First Law)
Στ=0 and ΣFx=ΣFy=0
τ = F⊥r

The Attempt at a Solution

 

[ideasrule]

Draw a free-body diagram of the ladder, being sure to include all forces. Then write out Newton's second law for both the horizontal and the vertical directions. For torque, choose a point and write out the rotational analogue of Newton's second law about that point.

 

[boomclapslap]

i've tried that, and it gets so complicated and there are so many unknown variables that I get lost every single time. this was actually on my test and i got 0.

 

[itr]

ladder is 3m from wall...it connects with the wall 4m high...so get the angle which is tan^-1 of 4/3...which is 53.1

then tan53.1=2umg/mg...which is equal to 2u..
tan53.1/2=coefficient friction=.67

i think that's how you do it