Posted by **kelsey** on Saturday, October 18, 2008 at 2:26am.

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

- physics help 4 please! -
**bobpursley**, Saturday, October 18, 2008 at 3:44am
I will be happy to critique your thinking.

- physics help 4 please! -
**drwls**, Saturday, October 18, 2008 at 4:23am
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

- physics help 4 please! -
**kelsey**, Monday, October 20, 2008 at 2:09am
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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