Posted by katie on .
ladder of mass m and length l leans against a frictionless wall at an angle of 60 degrees. The coefficient of static friction between the ladder and ground is 0.45. A man whose mass is 4 times the ladder climbs up. How far up the ladder can he go before he slips?

physics 
bobpursley,
Katie, you have two conditions that must be met.
1) the sum of forces in any direction is zero.
2) THe sum of moments about any point is zero.
So, draw the figure. Sum forces in horizontal, and vertical equations: that gives you two equations.
Sum moments about any point on the ladder, I suggest the base.
With these three equations, you have it.