Energy of translation and energy of rotation

[chloechloe]

Homework Statement

How would you go about figuring out the ratio of components (rotational and translational energy) of total kinetic energy?

Homework Equations

The Attempt at a Solution

i started with KEtotal=KEr+KEtr. KEr=1/2Iw^2; KEtr=1/2mv^2
use I for a disk-I=1/2mr^2
I put KEtr over KEr KEtr/KEr for a ratio

(1/2 mv^2)/1/2Iw^2
substitute in 1/mr^2 for I and v/r for w

(1/2 mv^2)/(1/2)(1/2mr^2)(v/r)^2

cancel m, v and r and 1/2

left with (1)/(1/2)

ratio is 2:1 KEtr:KEr ??

 

[Doc Al]

That's right. For a uniform disk that is rolling without slipping, the translational KE is twice the rotational KE. Good!

 

[chloechloe]

YAY! Thanks for confirming. I am struggling with physics.