Moment of inertia of a point mass

AI Thread Summary
The moment of inertia (I) of a point mass (m) is calculated using the formula I = m * r^2, where r represents the distance from the axis of rotation. This distance is crucial as it determines how the mass contributes to the rotational inertia about that axis. The moment of inertia must be referenced to a specific point or axis, with the minimum value occurring when the reference is through the center of mass (CM). For a point mass, the moment of inertia is zero when the axis of rotation passes through its location. Understanding these concepts is essential for analyzing rotational dynamics.
geekie weekie
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Hello,

This is a very basic question. Wikipedia says moment of inertia I of a point mass m is calculated as:

I = m * r^2

Where, r is distance from the axis of rotation. What this actually mean? I mean what is an r?
 
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geekie weekie said:
Where, r is distance from the axis of rotation. What this actually mean? I mean what is an r?

It is a distance, expressed in units of length (meters in the SI).
 
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this is axis of rotation and in front ist point mass not full stop .

it's at r dist from rod

I=mr2
 
moment of inertia of a point mass with respect to an axis is the product of mass times the distance of the axis
squared.So "r" is the distance of the mass "m" from the axis of roation.
 
Moment of Inertia of an object has to be referenced to a particular point or axis. Take any object and its MI is a minimum when that reference is through the CM. For a point mass, it is Zero.
 

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