How Do You Calculate the Rotational Inertia of a Wheel?

[nicolec08]

Hi everyone, I'm having a little trouble trying to answer this problem. Here it is:

A force of 22.04 N is applied tangentially to a wheel of radius 0.340 m and gives rise to an angular acceleration of 1.20 rad/s^2. Calculate the rotational inertia of the wheel.

Okay so i attempted the problem, here's what I got.

F=22.04
r= 0.340
m=?
$$\alpha$$=1.20 rad/s^2
$$\tau$$=Fxr = 7.49

And now I don't know where to finish. All I know is that you need torque to get the moment of inertia, and I need a mass to find the moment of inertia...Help me please!

 

[Doc Al]

And now I don't know where to finish. All I know is that you need torque to get the moment of inertia, and I need a mass to find the moment of inertia...Help me please!

If you have the torque and the angular acceleration, you don't need the mass to find the moment of inertia. Hint: How would you write Newton's 2nd law for rotational motion?

 

[nicolec08]

torque = Tdsin (theta)?

 

[Doc Al]

torque = Tdsin (theta)?

No, that's just the definition of torque.

Newton's 2nd law for translational motion is: F = ma

How would you write the equivalent law for rotational motion? Hint: What would F, m, and a be replaced with?