What is a moment of a Force?
As stated by the definition of moment above we can deduce, as we move a body with mass away from the axis of rotation on the pivot, the moment (or torque) increases.
The picture above demonstrates moment in action. If we increase d (distance of Garfield from the pivot) the moment will increase. Adding to it, if we would increase the weight F the moment will also increase.
This leads us to our formula:
Where, F is the force
and d is the perpendicular distance from the axis at point O to the line of action of the force.
Moment being a vector quantity
- Magnitude: The units for Moment are Nm or lbft. Magnitude can be determined using the formula mentioned above.
- Direction: The direction of the moment can be determined using the moment axis (RHR). the moment Axis is perpendicular to the pane that contains the force F and its moment arm d.
Moment Axis —–> Out of the page —–> Anti-Clockwise
Moment Axis —–> Into the page ——> Clockwise
For 2D problems, the resultant moment about a point can be determined by finding the algebraic sum of the moment caused by all the forces in the system.