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I'm trying to do a problem that goes something like this:

There is a mass (m) attached to one end of a massless rod (length l). The other end of the rod is attached to a frictionless pivot. The rod is released from rest at an angle F0 < pi/2. At what angle F does the force in the rod change from compressive to tension?

Attached is a diagram of the situation, as well as what I have done so far. I apologize for not putting my working out in the body of my post, but I haven't used LaTex before, and I don't have the time at the moment to learn how to use it.

Another thing: The problem should be done using a Lagrangian approach (although it isn't entirely necessary).

Any help would be highly appreciated!

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# Homework Help: Pendulum problem using Lagrangian approach

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