a uniform thin rod of length L and mass m is pivoted at one end the point is attached to the top of a car accelerating at a rate A.(adsbygoogle = window.adsbygoogle || []).push({});

a) what is the equilibrium angle between the rod and the top of the car?

b) suppose that the rod is displaced a small angle phi from the equilibrium derive the equation of motion for phi. Is the equilibrium angle stable or unstable?

I was able to get part a wich using newtons 2nd law for non inertial frames is

tan(equilibrium angle) = g/A.

but i am stuck on part b. I could use the lagrangian method to get phi(double dot) but that would be really messy, and was wondering if there would be a better way of getting it. oh and also he gave the hint to ignore air resistance and that torque= I*alpha.

thanks

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# Homework Help: Deriving an equation of motion

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