Torque Definition

In physics, torque is the external force that causes an object to rotate or around its axis. At the same time, force is a pull or push that changes the motion of an object. However, force tends to move an object in linear motion, whereas torque moves an object in angular motion. Moreover, an axis or axis of rotation is the point from where the object rotates. The Si unit to measure the torque is N.m, and usually, "T" is used to symbolize it. For instance, when an engine in a car revolves around its axis, it creates torque. Or when a force is applied at a door lock that causes the lock to rotate around its axis of rotation is an example of torque.


Table of Contents

Formula of Torque

The formula used to determine the torque is listed below:

\[\tau = r\;*\;F\;\sin \theta \]


\(\tau \) = torque

r = Lever arm (distance between the pivot and object's force point)

F = Force applied on an object

θ = Angle between vector force and the lever arm


If you want to calculate torque, you can use our Torque Calculator.


For more clear understanding, let us have an example below:

Suppose a force 120N is acting on a door's lock at 90°, whereas the lever arm is 0.5m long. Find the torque that applies to a lock.

Given data

F = 120N
r = 0.5m

To Find

Torque = ?


To find the torque, we can use the formula listed below:

\[\tau = r\;*\;F\;\sin \theta \]

Putting values in the formula:

τ = 0.5 x 120 x sin(90°)
τ = 60 N·m