# Moment of inertia of a point mass

by geekie weekie
Tags: axis, inertia, moment, rotation about axis
 P: 7 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?
PF Gold
P: 1,111
 Quote by geekie weekie 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).
 P: 49 _______________________________________________________________________ ___ this is axis of rotation and in front ist point mass not full stop . it's at r dist from rod I=mr2
P: 10

## Moment of inertia of a point mass

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.
 Sci Advisor PF Gold P: 11,352 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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