Question

A) What is the angular momentum of a 2.8 kg uniform cylindrical grinding wheel of radius 18 cm when rotating at 1500 rpm? B) How much torque is required to stop it in 6.0s
I know that the formula for angular momentum is L= Iw. Where I is the moment of inertia and w is the angular velocity about the axis of rotation. I don't know which numbers I could place for "I" and "w", or if have to find them! And I am lost over all with finding the torque. Please help!

Answer 1

Now I saw that the formula for torque is:
t=change in L/time
I still don't know how to get part A

Answer 2

You're going to have to calculate the moment of inertia of the disk. For a common geometry like a uniform cylinder, we just use a table. (One is found here: http://en.wikipedia.org/wiki/List_of_moments_of_inertia )

Observe that for a uniform solid cylinder, \[I = {mr^2 \over 2}\]

Your equation relating torque and angular momentum is correct.

Answer 3

I see now! Thank you so much! I have a test in my physics 1 class on Monday and the teacher gave us a few homework questions as a study guide so that's why I have been seeking help on openstudy! Again, thank you!