# Conservation of Angular Momentum: angular speed

by mickellowery
Tags: angular, conservation, momentum, speed
 P: 69 1. The problem statement, all variables and given/known data A student sits on a freely rotating stool holding 2 3.00kg dumbbells. When the students arms are extended horizontally the dumbbells are 1.00m from the axis of rotation and the student rotates with an angular speed of 0.750 rad/sec. The moment of inertia of the student and the stool is 3.00 kgm2 and it is assumed to be constant. The student pulls the dumbbells in to a position 0.300m from the rotation axis. What is the new angular speed? 2. Relevant equations I was going to try Ii$$\omega$$i=If$$\omega$$f but the problem with this is that the problem says I is constant at 3.00 kgm2. I assume that I need to factor in the radius somehow but I'm not sure how to do it. 3. The attempt at a solution
 P: 69 So can I model the dumbbells as a rod and use 1/12 ML2 as the moment of inertia or do I have to integrate $$\int$$$$\rho$$dV? I am facing problems with both ways, I don't know what the volume would be if I integrate, and it seems like modeling as a rod would not be correct.
 Quote by mickellowery So can I model the dumbbells as a rod and use 1/12 ML2 as the moment of inertia or do I have to integrate $$\int$$$$\rho$$dV? I am facing problems with both ways, I don't know what the volume would be if I integrate, and it seems like modeling as a rod would not be correct.