A dumbbell is made of two spheres, which each have a mass M and a radius r - and a massless stick af length L. Someone has placed a dumbbell so that it is standing complete upright, in its equilibrium position. The dumbbell is nailed in the center of the lower sphere, and this point therefore becomes axis of rotation. A small ball of mass m collides with the center of the stick at right angles in a totally inelastic collision with speed v.
What is the torque acting on the dumbbell when it is at the horizontal position?
Write up the corresponding equation in term of angular velocity.