on . Posted in Classical Mechanics

Moment, abbreviated as M, is the tendency to cause a body to rotate around an axis.  It is quantified by measuring force acting on the body and the distance from the axis.  When the moment exceeds the moment required to keep it in place, motion is developed.  In engineering statics, one of the fundamental principals is the sum of the moments about a point equal zero and there is no change in motion, the body is in static equilibrium.  In engineering dynamics, the sum of the moments about a point is equal to the mass times the acceleleration.

Moment Arm

A moment arm, also called lever arm or torque arm, refers to the perpendicular distance from a reference point or axis to the line of action of a force.  It plays a role in calculating moments or torques in rotational mechanics.  In the context of moments and torques, the moment arm represents the effective lever arm through which a force acts to produce rotational motion around a given axis.  It's the distance at which the force is applied from the axis of rotation, and it's essential for determining the torque or moment generated by that force.


Moment formula

\( M = F \;  d \)     (Moment)

\( F =  M \;/\; d \)

\( d =  M \;/\; F \)

Symbol English Metric
\( M \) = moment \(lbf\;/\;sec\) \(kg-m\;/\;s\)
\( F \) = force \(lbf\) \(N\)
\( d \) = length of arm \(in\) \( mm \)


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Tags: Force Moment