How Can Angular Momentum Principles Solve Disk Rotation Problems?

[tanglx61]

Hi people, I am pretty desperate because I have not the least idea of how to do two questions on my homework which is due for tomorrow..Please take a look and if you could do them, that's great, and if you could bother to explain them to me, i will appreciate it a lot!
Thank you! and here are the problems:
1.A uniform, solid disk with mass M and radius R is pivoted about a horizontal axis through its center. A small object of the same mass M is glued to the rim of the disk. If the disk is released from the rest with the small object at the end of a horizontal radius, find hte angular speed when the small object is directly below the axis.2. You are to design a rotating cylindrical axle to life 800-N buckets of cement from the ground to a rooftop 78.0 m above the ground. The buckets will be attached to a hook on the free end of a cable that wraps around the rim of the axle, as the axle turns, the bucket will rise.
A) what should the diameter of the axle be in order to raise the buckets at a steady 2.00 cm/s wen it is turning at 7.5 rpm?
B) If instead the axle must give the buckets an upward acceleration of 0.400 m/s^2, what should the angular acceleration of the axle be?

 

[kuruman]

Hi tanglx61, welcome to PF. Please observe the rules of this forum before seeking homework help.

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