# Rotational kinetic energy of a wheel

1. Dec 25, 2011

### richyr33

1. The problem statement, all variables and given/known data

I have a wheel with a diameter of 1.4m and the radius of gyration is 0.42m. The wheel has a mass of 13kg. Calculate maximum rotational kinetic energy.

2. Relevant equations

3. The attempt at a solution

From this all i can do is calculate the moment of inertia which is the mass (x) radius of gyration squared which gives me 2.29kg/m squared.
As far as i am aware i need the angular velocity to calculate the kinetic energy but i have no velocity figures. Any help is much appreciated

2. Dec 26, 2011

### Staff: Mentor

Without more information, there's not much you can do. Did you present the full problem exactly as given, word for word?

3. Dec 26, 2011

### mtayab1994

You have to know how many turns it took so you can use: $$\frac{1}{2}J_{\Delta}\omega^{2}=M_{\Delta}*\Delta\theta$$ to calculate the maximal angular speed.

Then you can just plug it in and find your answer .

Ps: JΔ of a wheel : $$J_{\Delta}=M*R^{2}$$

4. Dec 26, 2011

### richyr33

yes that is all the information that is in the question. I have previously calculated a maximum linear velocity which i now assume is what i have to use to answer the question even though it makes no reference to it. Many thanks for your replies.

5. Dec 26, 2011

### Staff: Mentor

So there are other parts to this problem? Post the entire problem, start to finish.