Kinetic Energy of Rolling Motion

1. Oct 18, 2007

Cici2006

1. The problem statement, all variables and given/known data
A 12g CD with a radius of 7.0 cm rotates with an angular speed of 35 rad/s.
What is its kinetic energy?

2. Relevant equations

3. The attempt at a solution
I used K=(1/2)mv^2(1+I/mr^2)
v=$$\omega$$r=(35rad/s)(0.07m)=2.45m/s
K=(1/2)(0.012kg)(2.45m/s)^2(1)=0.36

And it's wrong. Am i using the right formula? What should I do
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Oct 18, 2007

Staff: Mentor

For rotational KE, use:
$${KE} = 1/2 I \omega^2$$

3. Oct 18, 2007

Cici2006

I used that too and i still got it wrong.

4. Oct 18, 2007

Sourabh N

Are you keeping track of units. If its not the problem, just show your calculation

5. Oct 18, 2007

Cici2006

Oh I know what i did wrong now i forgot to multiply by 1/2. THanks for the help