Stability of a teeter-toy-classical mechanics

[Saph]

Homework Statement

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[/B]
In the image above, the toy consists of two identical mass hanging from a peg. we take the zero potential energy at the pivot.

Homework Equations

:[/B]
http://www.physicsmynd.com/?p=1172

The Attempt at a Solution

Since the potential energy is zero at the pivot, and the potential energy is defined by U(θ)=mgh, I had:
U(θ)= mg(- l*cos(α+θ)- l*cos(α-θ))
but the solution is: U(θ)= mg(L*cos(θ) - l*cos(α+θ)) +mg(L*cos(θ) - l*cos(α-θ))

So my question is,what is wrong with my answer, and why?

 

[TSny]

The zero of PE is at the pivot point.
l*cos(α-θ) is not the vertical distance between the pivot point and the mass on the right.

 

[Saph]

Thank you very much sir, I think my problem was with English more than it was with physics, I thought what he meant be pivot is the joining point of the arms with the peg, now I got the solution right.

 

[TSny]

OK. Good.

 

[ERK1]

Hello, could you please publish or send to me the correct solution to that example?

 

[ERK1]

Hello, could you please publish or send to me the correct solution to that example?

 

[haruspex]

Hello, could you please publish or send to me the correct solution to that example?

That's not how things are done here. If you have been given the same homework task and need help, please post your own attempt; maybe in a new thread.

 

[Bambisu]

Can someone do all my physics homeworks please and post them to me on time and not a minute late ?