Wall Climbing Force Problem

bob5000

In Victor Hugo's Les Miserables, the main character Jean Valjean, an escaped prisoner, was noted for his ability to climb up the corner formed by the intersection of two vertical perpendicular walls. Find the minimum force with which he had to push the walls (assume both hands are to exert the same force) whilst climbing. Assume that the coefficient of static friction is Uo.

I can't seem to solve this problem correctly. The hard part is determining the angle at which Jean is exerting the force to the walls. I thought it would be 90 degrees but he would be pushing downwards in order for it to be less difficult.

Doc Al

Here are a few hints. What vertical force must the walls exert on Jean? And what's the minimum normal force that must be exerted to create that much friction? (Don't forget Newton's 3rd law.)

bob5000

so the force would be F=mg/Uo?

quasar987

That's what I would have said, but the part when you say

disturbed me and I wasn't sure anymore. I still don't understand; what is your argument "against" 90° ??

bob5000

My professor said that this was a very difficult problem and that one like it would be on a quiz this week, so i figured it would'nt be that easy and thered be a trick in there somewhere about the angles of the walls or the angle hes pushing down at. I guess 90 degrees would work but would'nt it be easier to push downwards at like a 45 degree angle?

Doc Al

Maybe I'm missing something, but I don't think the problem is all that hard. Start by answering the questions I ask in my earlier post. (Don't try to guess the angle; you'll figure that out later.)