1. The problem statement, all variables and given/known data A student sits on a rotating stool holding two weights, each of mass 10 kg. When his arms are extended horizontally, the weights are 1 m from the axis of rotation and he rotates with an angular speed of 3 rad/s. The moment of inertia of the student plus the stool is 8 kg*m^2 and is assumed to be constant. If the student pulls the weights horizontally to 0.3 m on the rotation axis calculate (a) the final angular speed of the system and (b) the change in the mechanical energy of the system. 2. Relevant equations 3. The attempt at a solution I am not sure how to attempt this problem because I am confused by the statement "The moment of inertia plus the stool is assumed to be constant. " I thought that if the student brings its arms in it will change its moment of inertia so it can't be constant?