# Rotational Kinetic Energy - Clarification on what I need to solve for!

1. Jun 11, 2009

### grandprix

1. The problem statement, all variables and given/known data
A wheel (solid cylinder), mass of 13 kg and radius of 0.33m is initially at rest. The wheel undergoes an angular acceleration of 5 rad/s^2 for 18 seconds, rotating about its center axis (no translation). Find the Kinetic energy of the wheel at the end of the 1 seconds.

2. Relevant equations
KE = 1/2mv^2 + 1/2 I*w^2

3. The attempt at a solution
Okay so I was a little confused on whether I am finding the Total KE, or just th rotational KE.

If I were solving for total, KE = 1/2mv^2 + 1/2 I*w^2
First I need to solve for v, which I got to be 29.7, by employing the formula v=wr

I solved the equation for total KE and got 5765.438, where 5733.58 = 1/2mv^2 and 31.85 = is equal to 1/2 I W^2.

If I just needed to find the KE rot, then the answer would be 31.85.

2. Jun 11, 2009

### rock.freak667

The question does say no translation, so I assume you just need to get the rotational kinetic energy.

EDIT: How did you get so little rotational kinetic energy? Did you apply 1/2Iw2 correctly?

3. Jun 11, 2009

### grandprix

Thank you ! I may have done that wrong. I will chck it over