How Do You Calculate the Rotational Inertia of a Wheel?

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Homework Help Overview

The discussion revolves around calculating the rotational inertia of a wheel given a tangential force, radius, and angular acceleration. The subject area is rotational dynamics, specifically focusing on the relationship between torque, angular acceleration, and moment of inertia.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate the rotational inertia using torque and angular acceleration but expresses uncertainty about needing mass. Some participants question the necessity of mass in this context and suggest exploring Newton's 2nd law for rotational motion.

Discussion Status

The discussion is ongoing, with participants providing hints and prompting further exploration of the relationship between torque and moment of inertia. There is a focus on clarifying the application of Newton's laws in rotational dynamics.

Contextual Notes

Participants are navigating the definitions and relationships in rotational motion, particularly the role of torque and angular acceleration without explicit reference to mass. The original poster's confusion about the need for mass highlights a potential gap in understanding the concepts involved.

nicolec08
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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!
 
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nicolec08 said:
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?
 
torque = Tdsin (theta)?
 
nicolec08 said:
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?
 

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