Moment of inertia of a cylinder in unusual position

In summary, the conversation discussed how to find the moment of inertia for a thin disc with a perpendicular axis and a parallel axis passing through the center. The moment of inertia was determined to be 1/2mr^2 for the perpendicular axis and 1/4mr^2 for the parallel axis, which can be used to solve the problem by integrating the adjusted mass and distance values.
  • #1
24forChromium
155
7
True or false.jpg

See image. It would be better if you can show me the calculation process.

EDIT: the axis of rotation goes right through the centre of the cylinder.

NEVER MIND! GOT IT!
 
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  • #2
My opinion: for a thin disc whose radius is ##r## and mass is ##m,## with the axis perpendicular to the disc, the moment of inertia is ##I_0=\frac{1}{2}mr^2,## which may be easy to find. Then with the perpendicular axis theorem, if the axis is parallel to the disc and passes the center, the moment of inertia should be ##I_i=\frac{1}{2}I_0=\frac{1}{4}mr^2.##
With this result and the parallel axis theorem, we may be able to solve the problem. For the disc away from the center ##x##(based on your diagram), the disc's moment of inertia is ##\frac{1}{4}mr^2+mx^2##(of course ##m## should be adjusted. Then, just integrate them we may get the answer.
 

FAQ: Moment of inertia of a cylinder in unusual position

1. What is moment of inertia?

Moment of inertia is a measure of an object's resistance to changes in rotational motion. It is dependent on an object's mass and distribution of mass around its axis of rotation.

2. How is moment of inertia calculated for a cylinder?

For a cylinder in a usual position, the moment of inertia can be calculated using the formula I = 1/2 * m * r^2, where m is the mass of the cylinder and r is the radius.

3. What is considered an "unusual position" for a cylinder?

An unusual position for a cylinder refers to when the axis of rotation is not aligned with the central axis of the cylinder. This can include positions where the cylinder is tilted or at an angle.

4. How do you calculate moment of inertia for a cylinder in an unusual position?

To calculate moment of inertia for a cylinder in an unusual position, the parallel axis theorem can be used. This involves adding an additional term to the usual formula, which takes into account the distance between the axis of rotation and the cylinder's central axis. The formula becomes I = 1/2 * m * (r^2 + d^2), where d is the distance between the two axes.

5. Why is understanding moment of inertia important for a scientist?

Moment of inertia is an important concept in the study of rotational motion. It helps us understand how objects behave when they are subjected to a torque or force, and is crucial in the design of structures and machinery. It also has applications in fields such as physics, engineering, and astronomy.

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