Introductory Torque Statics Problem

AI Thread Summary
The problem involves calculating the torque on a 4.0-m-long, 24 kg pole supported at one end while being held 35 cm from the tip. The torque equation used is ∑τ=0, with the attempt to balance forces and torques leading to a calculation of F=-1344N, which seems excessively large. Participants in the discussion question the application of torques and suggest using the rightmost point as the pivot for simplification. There is confusion regarding the placement of the weight and the proper method for summing torques to achieve equilibrium. Clarifying these points is essential for solving the problem accurately.
JSmithDawg
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Homework Statement


You're carrying a 4.0-m-long, 24kg pole to a construction site when you decide to stop for a rest. You place one end of the pole on a fence post and hold the other end of the pole 35 cm from its tip.

I've drawn a diagram of the problem on Paint...
upload_2015-2-9_19-15-51.png


Homework Equations


∑τ=0
τ=F⊥r

The Attempt at a Solution


I know that ∑τ=F(r1)+w(r2)+N(r3)=0, and I'm going to rewrite it so F(r1)+N(r3)=-w(r2). Now, if I call the left-most point the pivot point, my new equation becomes F(.35m)+4m(9.8 N/kg * 24kg) =-2m(-9.8 N/kg* 24 kg), which simplifies to F(.35m) = -470.4Nm, which makes F=-1344N. This seems way too big to be right; what did I do wrong?
 
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it would be much easier to use the RIGHTmost point as the pivot. Where is the weight applied? ... why are you not adding torques to zero? ...
 
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