1. The problem statement, all variables and given/known data I've been working on this problem for several hours with no luck. Any help would be appreciated. (It's not homework) A thin rod of mass M and length L is hinged at the bottom, and almost balanced vertically. It starts to fall. Find the tangential component of the force that the part of the rod below r exerts on the part of the rod above r. (Theta is the angle between the rod and the vertical, r is the distance on the rod from the hinge) 2. Relevant equations SOLN: F = Mg(L-r)(3r-L)/(4 L^2) * Sin(theta) d x F = I *(angular acceleration) 3. The attempt at a solution I've already determined the angular acceleration to be 3/2 g/L Sin(theta) using the Lagrangian. I've calculated the moment of inertia to be: 1/3 M (L-r)/L [(L-r)^2 + 3*r^2] using the parallel axis theorem. I've tried for several hours to get the final equation for the force but I haven't been able to do so yet.... maybe there is a mistake in the moment of interia?