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August 20, 2014

Homework Help: Physics

Posted by COFFEE on Friday, March 30, 2007 at 4:16am.

A sanding disk with rotational inertia 1.1 x 10^-3 kg*m^2 is attached to an electric drill whose motor delivers a torque of 6 Nm about the central axis of the disk. What are the following values about the central axis at the instant the torque has been applied for 185 milliseconds?

(a) the angular momentum of the disk
_______ kg*m^2/s
(b) the angular speed of the disk
_______ rad/s


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my submitted answers were wrong.. and this is what i did/come up with.

185 ms = 0.185 seconds
2pi rad / 0.185 s = 33.96 rad/s (wf)

L = Iwf
L = (1.1 x 10^-3)(33.96)
L = 0.037356

.. am i missing something? .. what am i doing wrong? please show me, thanks!

You are missing the basic laws of motion.

Torque= inerita* angular acceleration
solve for angular acceleration, then.

wf= wi+ angular acceleration*time

angular momentum= I*wf

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