Equillibrium: torque and net force

AI Thread Summary
The discussion revolves around solving a physics problem involving torque and net force related to a ladder's equilibrium. The user calculated the total weight (f1) of the ladder and person as 885.92 N and established that horizontal forces (f2 and f3) must be equal. The challenge lies in determining the moment arm for the forces acting on the ladder, particularly whether the 0.7 meters can be used for the person's force. The user realizes that the ladder's length and height provide indirect angles necessary for calculating the moment arm. Clarification on these angles aids in resolving the problem effectively.
henry3369
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Homework Statement


http://imgur.com/rWsNsmp

Homework Equations


net torque = 0
net force = 0

The Attempt at a Solution


Finding f1 was easy.
f1 = wladder + person = 885.92 N
Then the horizontal forces are also equal:
f2 = f3

Now net torque = 0 (I'm using moment arm because there is no angle given):
f3(3.8) = wladder(moment arm) + wperson(0.70)

I can't manage to figure out the moment arm. I'm not sure if 0.7 meters can be used because I think that is the moment arm for the force of the person only. No angles were given, all I know is that the distance from the bottom of the ladder to the center of mass of the ladder is 2 meters.
 
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henry3369 said:
No angles were given
Oh, yes, they were (but indirectly). Length of ladder = 4m, vertical height of ladder = 3.8m.
 
Svein said:
Oh, yes, they were (but indirectly). Length of ladder = 4m, vertical height of ladder = 3.8m.
Didn't think about it that way. Thanks!
 

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