I'm kinda having trouble figuring out this problem...i already know that i have to use conservation of angular momentum Iiwi=Ifwf but i'm having trouble calculating the key part, the second moment of inertia. I'm pretty sure that im' supposed to be using this form of the calculation of inertia, I=Mr^2... but i still can't seem to solve it... like when i use it to test whether the numbers work out for the first moment of inertia 2.92 = 2.92*2 * 1.09^2, these numbers don't work out.(adsbygoogle = window.adsbygoogle || []).push({});

A student sits on a freely rotating stool holding two weights, each of mass 2.92 kg. When his arms are extended horizontally, the weights are 1.09 m from the axis of rotation and he rotates with an angular speed of 0.746 rad/s.

The moment of inertia of the student plus stool is 2.92 kg · m2 and is assumed to be constant. The student pulls the weights in horizontally to a position 0.307 m from the rotation axis.

Question: Find the new angular speed and find the kinetic energy before and after he pulls the weight inward.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Angular speed and intertia problem

**Physics Forums | Science Articles, Homework Help, Discussion**