The problem I am working on is: "A student sits on a freely rotating stool holding two dumbbells, each of mass 2.97 kg (see figure below). When his arms are extended horizontally (figure a), the dumbbells are 0.95 m from the axis of rotation and the student rotates with an angular speed of 0.740 rad/s. The moment of inertia of the student plus stool is 2.68 kg · m2 and is assumed to be constant. The student pulls the dumbbells inward horizontally to a position 0.298 m from the rotation axis (figure b). (a) Find the new angular speed of the student. b) Find the kinetic energy of the rotating system before and after he pulls the dumbbells inward. KE before KE after" I was able to solve the problem, the calculations being rather simple. My question is, does the act of extending your arms out, whilst grasping the dumbbells in your hand, cause you to have an angular speed? Or do you have to initially have an angular speed to see this changes in the angular speed occur? Also, the final and initial kinetic energy are not equal, why is that? Where did the energy go?