Asked by kelsey

A solid disk (mass = 1 kg, R=0.5 m) is rolling across a table with a translational speed of 9 m/s.

a.) What must the angular speed of the disk be?
? rad/s
b.) What is the rotational KE of the disk?
? J
c.) What is the total KE of the disk?
? J
d.) The disk then rolls up a hill of height 2 m, where the ground again levels out. Find the translational and rotational speeds now.
? m/s
? rad/s
Answered by bobpursley
I will be happy to critique your thinking.
Answered by drwls
The angular speed is w = V/R
I = moment of inertia = (1/2) M R^2
KE(rotational) = (1/2) I w^2
= (1/2)(1/2)M R^2(V/R)^2
= (1/4) M V^2

KE(ranslational) = (1/2) M V^2

Add the two KE types for total KE

Get to know these formulas. Others should not have to refresh your memory and do the work for oyu
Answered by kelsey
For some reason everytime I try to calculate the KE rotational I do not get the right answer. The translational speed can be used for V, right?
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