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Tuesday, October 12, 2010
Ch8 2 #4
12 comments:
Anonymous
said...
What formulas do we use for part one? I am having a lot of trouble with this problem.
I can't seem to get this one either. I think there should be 2 parts, 1 finding the I of her arms and the other of her whole body then either subtract or add them. But none of my answers work out
You do split it up into 2 parts, using I=f*MR^2 for both.
For her arms, use the equation I=MR^2 (where M=8 and R=.2) because her arms create a disk around the vertical axis (he mentioned in lecture that for a disk, f=1)
Then use I=(1/2)MR^2 for the rest of her body (M=56 because its total weight minus her arms and R=.2 again)Then add your 2 values for I together
12 comments:
What formulas do we use for part one? I am having a lot of trouble with this problem.
i am too i dont understand it at all
I thought to use I=mr^2 and the mass would be (64/8), but it was incorrect.
awfully nice of the prof. to just leave us helpless like this
I can't seem to get this one either. I think there should be 2 parts, 1 finding the I of her arms and the other of her whole body then either subtract or add them. But none of my answers work out
You do split it up into 2 parts, using I=f*MR^2 for both.
For her arms, use the equation I=MR^2 (where M=8 and R=.2) because her arms create a disk around the vertical axis (he mentioned in lecture that for a disk, f=1)
Then use I=(1/2)MR^2 for the rest of her body (M=56 because its total weight minus her arms and R=.2 again)Then add your 2 values for I together
hope this helps
Thank you very much to whomever posted the helpful comment above!
Thank You So MUCH Anonymous #6!
The answer comes out to be 1.4. I made f= 1/2 though. Not sure, but 1.4 definitely works.
f=1/2 is for the body (treated as a cylinder) and the other terms are for the arms.
is anyone else having a problem submitting their answers?? it won't let me submit my answers....
Agree with Anonymous #4 and like everyone else many thanks to Anonymous #6.
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