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Moment of Inertia Experiment

by massb
Tags: experiment, inertia, moment
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massb
#1
May15-12, 09:33 PM
P: 1
In my experiment based on the inertia the angular velocity or speed goes either up or down with the angular momentum remaining the same. I understand that when a person is rotating to change the inertia you would either extend or detract the arms and legs (think dancer). I understand this concept and even somewhat how the calculate it except my angular momentum.

L=Iw since my inertia is changing how do I find the changing w(angular momentum) if I don't know the value of the L(angular momentum) yet. Would I just physically count the number of rotations per second in radians for each time the inertia is changed?
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sk9
#2
May16-12, 06:22 AM
P: 16
Hi welcome to phy forum(everyone does that so i did it too for your first post)
Well you dont know the L now but i hope that you know the speed at which the dancer is expanding her/his arms(& her mass and her arms mass....etc). So you will calculate L(t) as a function output of time and you must know both L & w at some instant (maybe before after she moves her arms)simultaneously, this way you will know w(t).

NOOOOOOOO! dont count the number of rotation per second, I have no grudge over counting but it will give an average w over a time of 1 sec, which will be hazardous if w is not constant.
tiny-tim
#3
May16-12, 06:32 AM
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himassb! welcome to pf!
Quote Quote by massb View Post
In my experiment I understand this concept and even somewhat how the calculate it except my angular momentum.

L=Iw since my inertia is changing how do I find the changing w(angular momentum) if I don't know the value of the L(angular momentum) yet. Would I just physically count the number of rotations per second in radians for each time the inertia is changed?
angular momentum is difficult to measure directly (if you don't know the moment of inertia)

the only convenient way i can think of is to transfer all the angular momentum to a "reference" body
what exactly is your experimental set-up?


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