1. A rigid rod of mass M and length L rotates in a vertical plane about a frictionless pivot through its center of mass. Particles of masses m1 and m2 are attached at the ends of the rod. Determine the angular acceleration of the system when the rod makes an angle θ with the horizontal. In the accompanying picture, m2 is obviously larger and the rod is rotating clockwise. 2. τ=Iα=Frsinθ 3. The inertia I calculated for the system is (M/12 + (m1 + m2)/4)L2. I think that the angle between position vector r and the force F would be 90 - θ. So then the angular acceleration α would be m2g(L/2)sin(90 - θ) / I? I'm confused about whether or not the force of gravity on m1 also needs to be taken into account and if so, how.