Two masses (mA= 2 kg, mB= 4 kg) are attached to a (massless) meter stick, at the 0 and 75 cm marks. The system is then hung from a string, so that it stays horizontal. Now, if mass B was removed, and no additional force was supplied, calculate the size of the angular acceleration of the meter stick at that instant. I calculated the center of mass to be at the 50 cm mark, but I don't know how to get the angular acceleration. Do I just use +rF/mr^2 = angular acceleration? I got the wrong answer form that. This seems like a simple problem, but maybe I'm thinking too much..