Difficult Ladder Against Wall Torque Problem

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The discussion revolves around a physics problem involving a ladder leaning against a wall, where an 85 kg person stands on a 6.6 kg ladder. The user has calculated the normal force from the ground (f1) as 898.6 N but is struggling to find the frictional force (f2) and the normal force from the wall (f3), which are believed to be equal. There is confusion regarding the application of the friction formula, as the coefficient of friction is not provided. Participants suggest focusing on torque calculations, particularly around the base of the ladder, to simplify the problem. The conversation emphasizes the importance of correctly setting up torque equations to find the unknown forces.
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Difficult Ladder Against Wall Torque Problem!

Homework Statement


An 85 kg person stands on a uniform 6.6 kg ladder that is 3.9 m long, as shown. The floor is rough; hence it exerts both a normal force, f1, and a frictional force, f2, on the ladder. The wall, on the other hand, is frictionless; it exerts only a normal force, f3. Using the dimensions in the figure, find the magnitudes of f1, f2, and f3.

Homework Equations


All forces and torque formulas.

The Attempt at a Solution


I found f1 - 898.6 N. I can't find f2 and f3, which I think are supposed to be equal. No matter what I try, I can't seem to get an answer. Here's my work:

16hok91.jpg


Help please? Thanks in advance.
 
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Have you tried applying f = μN, where f is the frictional force and N is the normal force? Where you given the coefficient of friction, μ?
 


No; I wasn't given the coefficient of friction. My instructor, for all of our problems relating to torque, has made it clear that we do not need to apply f = μN.
 


Alright. At the end of your work it looks like you wrote "f3 = 698.1N". Is this not what you were looking for?
 


That is what I was looking for, but that's an incorrect answer.
 


Got it. Just one last question; how far up (or down) the ladder does the problem say the man is standing?
 


That information is not given.

Here is the diagram that goes along with the problem:

11-3ae.gif
 


Great. It is hard to see your work in the picture, but try solving for the torque around the top of the ladder. Show me the equation you set up. I got to a different answer.
 


Find the torque (moment) about the contact point at the bottom of the ladder. It doesn't involve f1 or f2 and it doesn't depend
upon the person's distance up the ladder.
 
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