What is Moment of Force? - Definition, Formula, Classification, Examples

By Deepak Yadav|Updated : August 30th, 2022

Let's first understand the fundamentals of force before diving into the specifics of the moment of force. A force is an influence with the capacity to change the motion of an object. A force acting on an object with mass can cause it to accelerate or alter its velocity. An easy way to describe force is as a push or a pull. Since a force has both magnitude and direction, it is a vector quantity. It is expressed as a newton (N) in the SI system. F is the symbol used to denote force.

The rotational impact of a force is known as the moment of force, which is defined as the force times the perpendicular separation between the force and a pivot. The moment of force depends on its magnitude and the perpendicular separation between it and the pivot. The twisting impact increases as perpendicular distance increases (moment).

Table of Content

Define Moment of Force

The moment is the term used to describe the turning effect of a force. It is the result of multiplying the force by separating the force's line of action and the pivot point or point at which the object will turn. The SI unit for the moment of force is the Newton-meter (Nm). It is a vector quantity.

The right-hand grip rule, which is parallel to the plane of the force and has a pivot point parallel to the axis of rotation, determines its orientation. 

Moment of Force Formula

The moment is defined as a force's turning effect. It is the result of multiplying the force by the separation between the force's line of action and the pivot point or point at which the object will turn. It is denoted by 𝝉.

𝝉 = F×d

Where,

 𝝉 is the moment of force

F is the force

d is the perpendicular distance between the force's line of action and the pivot.

Classification of Moment of Force

The moment of force refers to the effect of a force on a body rotating around an axis. It is equal to the product of the force's magnitude and the line of force's perpendicular distance from the axis of rotation. The moment of force is classified into the following categories:

  • Turning moment
  • Bending moment
  • Twisting moment

Turning moment

This moment causes a body to revolve around a fulcrum. The body can freely rotate around a fulcrum in this scenario.

Bending moment

This moment causes a body to bend around one of its fixed ends.

Twisting moment

This event causes a shaft to twist around one of its fixed ends.

What is the SI Unit of Moment of force?

The tendency of a force to make a body rotate around a particular point or axis is measured by its moment of force.

Moment of force = (force) * (perpendicular distance from the pivot)

Newton is the SI unit of force, whereas a meter is the SI unit of distance. so, Newton-meter is the S.I. unit of moment of force.

The Direction of the Moment of Force

In its simplest form, a moment is created by multiplying the distance to a point by a physical quantity (such as force). It is categorized into two types based on the direction of the moment.

  • Clockwise Moment
  • Anticlockwise Moment 

Clockwise Moment

The moment created is referred to as a clockwise moment if a force acting on a body tends to cause the body to rotate in a clockwise direction.

Anticlockwise Moment

An anticlockwise moment is created when a force acting on a body has the potential to cause the body to rotate counterclockwise.

Examples of Moment of Force

A moment results from a force rotating around a pivotal fixed point. A door opening around a fixed hinge, seesaws, scissors, or a spanner revolving around a nut are a few examples.

  • To open and close a door, a force (push or pull) normal to the door is applied at the handle P, which is the farthest away from the hinge.
  • For the upper circular stone of a hand flour mill to be readily turned about the iron pivot at its center by providing a modest push at the handle, it is equipped with a handle near its rim (i.e., maximum distance from the center).
  • A force is exerted tangentially on the rim of the wheel to turn the steering wheel.
  • On a bicycle, a slight force is given to the pedal of a toothed wheel to turn the wheel counterclockwise.
Important Topics for GATE Exam
Composite BeamsCompression Members
Concurrent Force SystemConditions for Deadlock in Operating System
Conduction Heat TransferConsensus Theorem
Constants in CConvection Heat Transfer
Coplanar Force SystemCut Set Matrix

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FAQs on Moment of force

  • The result of multiplying the force's component perpendicular to the line of distance by the distance between the point and the point of application is known as the moment of a force.

  • Moment of force = F x d

    The moment of a force is given in Newton meters (Nm), where F is the applied force and d is the distance from the fixed axis. For both balanced and unbalanced forces, the moment of force can be calculated using the moment of the force formula.

  • As an example, visualize opening a door. The door revolves around its hinges when you pull on the door handle (the hinges are a pivot). The rotation of the door was a direct result of the force you applied when you pushed it open.

  • For example, the moment of force, also known as torque, is the result of the force acting on an object and the item's distance from the reference point. Any physical quantity can theoretically be multiplied by a distance to create the moment of a force.

  • While the moment measures the angle between the point of rotation and the force's line of action, torque measures the force that turns a body. The tendency of a force to cause a body to rotate at a particular point or axis is described in physics as the moment of a force.

  • The magnitude and distance from the rotational axis of a force determine its moment. The moment of a force about a point is (the force's magnitude)×(the perpendicular distance of the line of action of the force from the point).

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