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
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.
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.
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.
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.
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.