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aweeeezy
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Homework Statement
Here's a screen shot of the problem statement:
http://i.imgur.com/IRI02Ne.png
For the purpose of this post, I'll label the given information as:
a = left side of ladder (2.5m)
a' = distance from floor to the point where the man is standing (2.0m)
b = right side of ladder (2.5m)
c = distance between the feet of the ladder (1.8m)
m = mass of man (78kg)
T = force of tension on the horizontal support of the ladder
T_A = torque on the left foot of the ladder
T_B = torque on the right foot of the ladder
T_C = torque on the hinge of the ladder
N_l = normal force of the ground against the left foot of the ladder
N_r = normal force of the ground against the right foot of the ladder
N_man = normal force of the step against the man
Using the law of cosines, I found:
angles A and B = 68.9 degrees
angle C = 42.2 degrees
I know FBD must be drawn for each side of the ladder
I know that N_man = mg
I know that T = the horizontal component of mg
I know that net torque = 0 and net forces are 0 also
I'm having a really hard time mapping out where all the forces are and where equilibrium actually exists...even after looking at similar post like this one: https://www.physicsforums.com/threads/triangle-ladder-equilibrium-problem.796257/
I'm really disappointed that I can't figure this out even though there's all this information.
Homework Equations
net torque = 0
net forces = 0
The Attempt at a Solution
Here's a terrible FBD of the left hand side: https://sketch.io/render/sketch55467fe4bc86c.png
T_A = r x F = a' * cos(68.9) x (78)(9.8) = 550.3 N
T_C = r x F = 0.5 * sin(C/2) x (78)(9.8) = 137.6 N
T_B = ... (this part doesn't make sense to me)
I'm so frustrated and confused at this point.
Where is the force `R` coming from in the similar post I linked to?! Why does N_l exist if mg is canceled out by N_man?!