 #1
FluffCorgi
 3
 0
 Homework Statement:

A 65kg student is ice skating as shown. She is initially rotating at with an angular speed of 2.5rad/s with her arms straight out. At this time she can be modeled as a vertical and horizontal cylinder as shown.
She then brings her arms in, at which point she can be modeled as only a vertical cylinder with the properties shown.
The moment of inertia for the vertical cylinders spinning around their axes is I = 1/2mr2.
The moment of inertia for the horizontal cylinder spinning around it's center, perpendicular to it's axis is I = (1/12)md^2.
Determine all of the following moments of inertia, angular speeds and angular momenta relative to the axis of rotation.
 Relevant Equations:

arms
m = 6kg
d = 1.7m
core
m = 59kg
r = 0.18m
full body
m = 65kg
r = 0.18m
I have the moment of inertia for the core(initial) and full body(final) but my answer for the moment of inertia for the arms(initial) was incorrect.
Arms(initial) moment of inertia:(1/12)(6)(1.7^2)=1.445 this is incorrect for some reason
Core(initial) moment of inertia: .9558
Full Body(final): 1.053
I also have to find the angular velocity and I have done this correctly for the arms and core but I could not figure out how to find the angular velocity for the full body(final)
Arms: 2.5 rad/s
Core: 2.5 rad/s
Full Body(final): I don't think I can solve this without the arms initial moment of inertia
Angular Momentum
Arms: my moment of inertia was incorrect so this was as well
Core: 2.3895
Full Body(final): My moment of inertia for the arms was incorrect so this was as well but this was my work to attempt to find it.
(1.445+.9558)2.5 = (1.053)w
w = 5.699 this was wrong but i tried to solve it anyway
I need help with the initial moment of inertia for the arms.
Arms(initial) moment of inertia:(1/12)(6)(1.7^2)=1.445 this is incorrect for some reason
Core(initial) moment of inertia: .9558
Full Body(final): 1.053
I also have to find the angular velocity and I have done this correctly for the arms and core but I could not figure out how to find the angular velocity for the full body(final)
Arms: 2.5 rad/s
Core: 2.5 rad/s
Full Body(final): I don't think I can solve this without the arms initial moment of inertia
Angular Momentum
Arms: my moment of inertia was incorrect so this was as well
Core: 2.3895
Full Body(final): My moment of inertia for the arms was incorrect so this was as well but this was my work to attempt to find it.
(1.445+.9558)2.5 = (1.053)w
w = 5.699 this was wrong but i tried to solve it anyway
I need help with the initial moment of inertia for the arms.