Courses
Courses for Kids
Free study material
Offline Centres
More
Store Icon
Store

Difference Between Torque and Moment

ffImage
Last updated date: 24th Jul 2024
Total views: 63.9k
Views today: 1.63k
hightlight icon
highlight icon
highlight icon
share icon
copy icon

What is Torque in Physics?

Torque is defined as the measure of the force that can cause an object to rotate about an axis. Force is the thing that causes an object to accelerate in linear kinematics. Like in that way, torque causes an angular acceleration. So, torque can be defined as the rotational equivalent of linear force. And the point where the object rotates is called the axis of rotation. Basically, according to physics, torque is simply the tendency of a force to turn or twist. Different terms like moment or moment of force are widely used to describe torque. Generally, torque refers to the twisting force that causes motion and it also refers to the turning effect. 

Basically, the point of the rotation of the object is called the axis of rotation. Everyone is making use of this force without realizing this fact. And also the Torque is a vector quantity. So, the direction of the torque vector depends on the direction of the force on the axis. Torque can either be defined as static or dynamic.

Static torque: A static torque is the type of torque that does not produce an angular acceleration. For Example, If Someone is pushing on a closed-door they are applying a static torque to the door because the door is not rotating about its hinges, despite the force applied. If someone is pedaling a bicycle at a constant speed they are also applying a static torque because they are not accelerating.

Dynamic torque: A dynamic torque is the type of torque that produces an angular acceleration. For Example, the drive shaft in a racing car accelerating from the start line is carrying a dynamic torque because it must be producing an angular acceleration of the wheels given that the car is accelerating along the track.

Measurement of Torque

The unit of torque for measuring the value is Newton–meter (N-m). This equation can be represented as the vector product of force and position vector.

= r x F

So, this equation is defined as a vector product hence torque also must be a vector.

Introduction to Moment 

The Moment of a force is a type of measure of its tendency to cause a body to rotate about a specific point or axis. This force is different from the tendency for a body to move, or translate, in the direction of the force. For developing a moment, the force must act upon the body in such a manner that the body would begin to twist and this will occur every time a force is applied so that it does not pass through the centroid of the body. A moment basically generates due to a force not having an equal and opposite force directly along its line of action.

Elements of a Moment

In the Elements of a moment, it is described that the magnitude of the moment of a force acting about a point or axis is directly proportional to the distance of the force from the point or axis. So, the Moment is defined as the product of the force (F) and the moment arm (d). The moment arm is the perpendicular distance between the line of action of the force and the center of moments. 

Moment = Force x Distance 

M = (F)(d)

So basically, the turning effect of a force is called the moment. The moment is the result of the force multiplied by the perpendicular distance from the line of action of the force to the pivot or point where the object will turn.

Measurement of Moment 

The SI unit of moment of a force is Newton-meter (Nm) and It is a vector quantity. Moment’s direction is given by the right-hand grip rule perpendicular to the plane of the force and pivot point which is parallel to the axis of rotation.

=F×d

In this particular moment concept, the moment arm is defined as the distance from the axis of rotation. This perpendicular distance plays an important role. For Example, The lever, pulley, gear, and most other simple machines create mechanical advantage by changing the distance and that is the moment arm.

Torque Formula derivation

て = F × r × sinθ

て = torque

F = linear force

r = distance measured from the axis of rotation to the point where the application of linear force takes place

theta = the angle between F and r

In this particular formula, sin(theta) has no units, r has units of meters (m), and F happens to have units of Newtons (N). 

Combining all these units together, it can be seen that a unit of this force is a Newton-meter (Nm).

The Formula Derived as: The SI unit for torque is newton-meter (N⋅m).

Now to find out the formula or expression.

Rate of change of Angular Momentum in relation to time = \[\frac {\Delta L} {\Delta T}\]

Now,\[\frac {\Delta L} {\Delta T} = \frac {\Delta\lgroup I\omega\rgroup} {\Delta T} = \frac {I.\Delta\omega} {\Delta T}\] ……. (1) 

Here I is the constant when mass and shape of the object are unchanged

Now \[\frac {\Delta \omega} {\Delta T}\] refers to the rate of change of angular velocity with the time that is angular acceleration (α).

So from equation 4, \[\frac {\Delta L} {\Delta T}\] = I α …………………(2)

I i.e, a moment of inertia, refers to the rotational equivalent of mass(inertia) of linear motion.

Similarly, the angular acceleration α (alpha) refers to the rotational motion equivalent of linear acceleration.

So from equation 5, \[\frac {\Delta L} {\Delta T}\] = τ ……………………. (6) 

This describes the rate of change of angular momentum with time called Torque.

Torque refers to the moment of force. 

Torque (て) = r x F 

                   = r F sinθ ……………. (3)

F is the force Vector and r refers to the position vector

θ happens to be the angle between the force vector and the lever arm vector. ‘x’ certainly denotes the cross product.

て = r F sin θ = r ma sinθ = r m αr sinθ =

𝑚r2.

α sin θ = I α sinθ = I X α ……………………… (4)

(α is angular acceleration, I refers to the moment of inertia and X denotes cross product.)

て = I α (from equation 4)

or, て= \[\frac {I\lgroup \omega2-\omega1\rgroup} {t}\] (here α = angular acceleration = time rate of change of the important angular velocity = \[\frac {\lgroup \omega2-\omega1\rgroup} {t}\] where ω2 and ω1 happen to be the final and initial angular velocities and t is the time gap)

or, て t = I (ω2-ω1) ……………………(5)

when, て = 0 (i.e., net torque is zero),

I (ω2-ω1) = 0

i.e., I ω2=I ω1 ………….. (6)

Difference between Torque and Moment 

Torque

Moment

Torque is the measurement of the turning force of an object

Moment is the measurement of the perpendicular distance from the point of rotation to the force’s line of action

The symbol of torque is, τ

and SI unit is Nm/revolution

The symbol of the moment is M and SI unit if NM

Torque is a movement-related force

Moment is a static force

Torque is basically used to measure the coupling

The moment is not at all used for this purpose

Torque is used where there is an availability of a pivot and rotation

Moment is produced by any lateral force and used in non-rotational events

Torque refers to the nature of the force to rotate the object in a pivot.

Moment is referred to the nature of the force to move the object

Torque is the tendency of a force to rotate an object in a pivot.

Moment is a concept of engineering and physics that refers to the tendency of a force to move an object

Torque is a measure of the turning force of an object.

Moment is the perpendicular distance between the point of rotation and the force’s line of action

FAQs on Difference Between Torque and Moment

1. Why is Rotational Motion Considered the Toughest and an Important Topic in Mechanics?

Rotational motion is considered the toughest topic because it requires a great intuition with deep subject knowledge. Torque is one of the topics that is preferred not only at school-level exams but also in higher-level exams; that’s why it becomes an important topic in mechanics.

2. To Maintain the Rotation of the Shaft at an Angular Speed of 300 rad/s, and the Engine Should be Offered a Torque of 280 N.m. Determine the Power Required in the Same.

Given data:

て=  280 N.m


ω = 300 rad/s


To determine: P


So, using these values in P = てω


P = 300 x 280 = 84000 W or 84 kW

3. Why the Handle of a Screw Gauge Made Wide?

According to the below equation, F ∝ 1/r


て = F x r


To get an effective turning effect of a screw gauge with less effort (applying force), its handle is made wide to keep the distance ‘‘r’ larger.

4. Is Torque a Power?

No!


Torque is the capacity to perform any task, while power is the rate of doing work or applying torque to generate a turning effect in the body.

5. Define Torque?

Torque is defined as the measure of the force that can cause an object to rotate about an axis. Force is the thing that causes an object to accelerate in linear kinematics. Basically, according to physics, torque is simply the tendency of a force to turn or twist. Different terms like moment or moment of force are widely used to describe torque. Generally, torque refers to the twisting force that causes motion and it also refers to the turning effect. 

6. Define Moment?

The Moment of a force is a type of measure of its tendency to cause a body to rotate about a specific point or axis. So basically the turning effect of a force is called the moment. The moment is the result of the force multiplied by the perpendicular distance from the line of action of the force to the pivot or point where the object will turn.

7. What are the applications of Torque?

The applications of Torque are: If there is any object that is experiencing torque, there is a pivot point. Few applications are provided for the torque: Seesaws and Wrenches, Gyroscopes, A pendulum or a parachute is applying torque when swinging, A person riding a bicycle, Flag flying on a mast.

8. What is the difference between Torque and Moment?

The difference between torque and Moment are: Torque is the measurement of the turning force of an object while Moment is the measurement of the perpendicular distance from the point of rotation to the force’s line of action. Torque is basically used to measure the coupling while The moment is not at all used for this purpose. Torque is a movement-related force while Moment is a static force.

9. From where can students find all the study materials for the concept of Torque and Moment?

Students can easily find all the study materials for the concept of Torque and Moment from the Vedantu app or website. All the materials are there and any student can easily access it. It is totally free of cost. Students only need to sign in and can find all the study materials for all the concepts prepared by the professionals and in a very easy and simple way for easy understanding.