# Angular Momentum Problem: Rotation Rate [Solved]

JoeyBob
Homework Statement:
See attached
Relevant Equations:
L=rotation rate*I
First I found the moment of inertia,

I=1.8(5.5^2+3.9^2+4.9^2)

=125.046

Then I tried to find the rotation rate using the equation L=rotation rate*I

rotation rate=3773/125.046=30.173

But the answer is suppose to be 21.263?

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First I found the moment of inertia,

I=1.8(5.5^2+3.9^2+4.9^2)
No. The rotation is about the z (k) axis. What are the distances from that axis?

JoeyBob
No. The rotation is about the z (k) axis. What are the distances from that axis?

Doesn't k hat represent how far something is from the z axis?

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Doesn't k hat represent how far something is from the z axis?
No, it is how far it is along the z axis. And you mean the coefficient of ##\hat k##. ##\hat k## is the direction of the z axis.

Steve4Physics and JoeyBob
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You have to use pythagorean theorem on the i and j coordinates to find the distance from the z-axis.

JoeyBob
JoeyBob
No, it is how far it is along the z axis. And you mean the coefficient of ##\hat k##. ##\hat k## is the direction of the z axis.
You have to use pythagorean theorem on the i and j coordinates to find the distance from the z-axis.
Yes.