Moments of Inertia for a Cylinder and Disk

In summary, the moment of inertia of an object can vary depending on the choice of axis it rotates about. There is some confusion as to the correct equation for calculating moment of inertia for a cylinder or disk, but it ultimately depends on the axis of rotation. The link provided explains this concept in more detail.
  • #1
johnhuntsman
76
0
What are they? I have some poeple telling me that for a cylinder it's I = (1/4)MR2 + (1/12)ML2 and that for a disk it's the same. Other people have told me that it's I = (1/2)MR2 for a disk and that it's the same for a cylinder. In the past I've used the former and have gotten the right answers on my homework but I used the same equation for a question I'm stuck on and got the incorrect answer. I just want some clarification on this, I'd really appreciate it.
 
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  • #2
The moment of inertia of an object depends on the choice of axis that it rotates about.
http://www.tutorvista.com/content/physics/physics-iii/rigid-body/moment-inertia-rod.php
 
  • #3
TSny said:
The moment of inertia of an object depends on the choice of axis that it rotates about.
http://www.tutorvista.com/content/physics/physics-iii/rigid-body/moment-inertia-rod.php

Ah. I didn't see that I was using the equation for a cylinder about a diameter. Thanks. I appreciate it : D
 

FAQ: Moments of Inertia for a Cylinder and Disk

What is the definition of moment of inertia?

Moment of inertia is a measure of an object's resistance to changes in its rotational motion, and it depends on the object's mass, shape, and distribution of mass.

How is the moment of inertia different for a cylinder and a disk?

The moment of inertia for a cylinder and a disk is different because they have different shapes and distributions of mass. A cylinder has a greater moment of inertia than a disk because it has more mass distributed farther from its axis of rotation.

How does the moment of inertia affect an object's rotational motion?

The moment of inertia affects an object's rotational motion by determining how much force is required to change its rotational speed or direction. Objects with a larger moment of inertia will be more resistant to changes in their rotational motion.

How can the moment of inertia be calculated for a cylinder or disk?

The moment of inertia for a cylinder or disk can be calculated using the formula I = ½MR², where I is the moment of inertia, M is the mass of the object, and R is the radius of the object.

Are there any real-world applications of moments of inertia for cylinders and disks?

Yes, moments of inertia for cylinders and disks are important in engineering and physics for understanding the rotational motion of objects such as wheels, gears, and flywheels. They are also used in sports equipment, like the rotation of a discus or the spin of a figure skater.

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