Kinetic Energy of Rolling Motion

AI Thread Summary
The discussion revolves around calculating the kinetic energy of a rotating CD with a mass of 12g and a radius of 7.0 cm, rotating at an angular speed of 35 rad/s. The user initially applied the formula K=(1/2)mv^2(1+I/mr^2) but made an error in the calculation, resulting in an incorrect answer. After receiving feedback, they realized they forgot to multiply by 1/2 in their calculations. The correct approach for rotational kinetic energy is to use K = (1/2) I ω^2, highlighting the importance of careful unit tracking and formula application. The user ultimately corrected their mistake with assistance from others in the discussion.
Cici2006
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Homework Statement


A 12g CD with a radius of 7.0 cm rotates with an angular speed of 35 rad/s.
What is its kinetic energy?


Homework Equations





The Attempt at a Solution


I used K=(1/2)mv^2(1+I/mr^2)
v=\omegar=(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
 
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For rotational KE, use:
{KE} = 1/2 I \omega^2
 
I used that too and i still got it wrong.
 
Are you keeping track of units. If its not the problem, just show your calculation
 
Oh I know what i did wrong now i forgot to multiply by 1/2. THanks for the help
 
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