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Moment and Turning Effect of Force for JEE

What is the Turning Effect of Force?

Last updated date: 22nd Mar 2023
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When force is applied to the object in such a way that an object starts moving in a circle about a pivot point is called the turning effect of force. This turning effect of the force is called the moment of the force. The force can move the object in a clockwise or in an anti-clockwise direction about a pivoted point which depends upon the direction of the force. An example of a moment of force used in everyday life is when we apply a pushing force at the end of the door to open it.

The force required to rotate a body about a pivoted point is known as torque. Torque is a vector quantity. It is the reason behind the angular acceleration of the object. In this article, an attempt has been made to provide a brief conceptual knowledge about the effect of force, examples of turning effect of forces, factors affecting the turning effect of force, formula of turning effect of force, etc.

Mathematical Formulation of the Moment of Force

For the derivation of the relationship of the turning effect of force, consider an object having a beam-like structure whose one end is pivoted. When the force F is applied to the free end of the beam at a distance of “r” from the pivoted end (where “r” belongs to the perpendicular distance from the pivoted point), then a turning effect will be developed due to the application of the force.

Image: A representation of a moment of force

Mathematically, it is derived as,

Moment of force = Applied force $\times$ perpendicular distance from the pivoted point

$M=F\times r$

The S.I unit of the moment of force is Newton-meter (N-m), the applied force is in Newton (N), and the perpendicular distance is in meter (m).

There is a sign convention regarding the concept of moment of force. The moment of force in a clockwise direction will be negative, while the moment of force in an anti-clockwise direction will be positive.

Factors Affecting Turning Effect of Forces

There are various factors on which the turning effects of the force depend. These factors affect the moment of the force as a result to a great extent. Such factors are given below:

• The magnitude of applied force

The applied force is directly proportional to the moment of force. As the force increases, the moment of force will increase. In the same case, if the applied force is decreased, the moment of force will also decrease. In this way, the moment of force will be affected due to the magnitude of the applied force.

• The perpendicular distance from the pivoted end

The perpendicular distance between the applied force and the pivoted point greatly affects the moment of force. If the distance between the applied force and the pivoted point is less, then it is difficult to obtain a large moment of force. When the force is applied far from the pivoted point, then it will result in a large magnitude of turning effect of force.

Difference Between Moment of Force and Torque

Moment of Force and Torque are often confused together. They have the same meaning in physics but slightly distinct meanings in mechanics. While both share the same unit, N-m, the moment is a static force while the torque is a moving force. Moment is employed when there is no rotation, but torque is used when there is. We will look at the difference between them below.

 Sr. no. Moment of Force Torque Moment of force refers to the measurement of the perpendicular distance from the pivot point or the point of rotation to the line of action of the force. Torque refers to the measurement of the turning force that acts on a body or an object. Moment of force is a static force and does not depend on movement. Torque on any body is related to its movement. Moment of force is a concept used in engineering and physics and it refers to the tendency of any force to move an object. Torque is a measure of the tendency of any force to rotate an object in a pivot or about an axis of rotation. The SI unit of moment of force is Nm. The SI unit of moment of force is Nm.

Examples of Moment of Force

There are various examples of the turning effect of force, that are mentioned below:

• When a force is applied for pushing or pulling, the action of the door generates a moment of force on the door which opens or closes the door.

• When two people sit on a see-saw, then force is applied by the heavier person about a pivot point, which generates an equivalent moment of force that lifts the other person to the other side.

• When a force is applied to the handle of the bicycle to take a turn about a perpendicular axis, then the moment of force will be generated about the axis of the handle of the bicycle.

Conclusion

This article concludes with interesting information regarding the concept of turning effects of force, which is known as the moment of force. The article starts with the clarification of the first query, i.e., what is the turning effect of the force? This article explains the turning effect of force examples, factors affecting the turning effect of force, and the turning effect of force examples. This article has also explained the entire concept of turning effects of force along with a diagrammatic point of view for a better visualization and understanding of the concept.

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FAQs on Moment and Turning Effect of Force for JEE

1. What is the effect of the forces?

Whenever a force is applied to the object, there are some effects reflected on the object with respect to its dimensions, position, etc. Such changes occurring in the object will be termed as the effect of force. The effect of force completely depends upon the nature of the force and the application point of force on the object. When the force is applied along the dimension of the object, then the object will translate. If the applied force is acting perpendicular to the axis of the object, it will rotate.

2. What is the weightage of this topic in the JEE exam?

The weightage of the current topic titled “moment of force” is 4-5%. This concept is introduced in the section on kinematics, which has a large variety of important concepts for the JEE examination. Nearly 5-6 questions can be expected in the given competitive examination of JEE. It is necessary to practise many questions in preparation for the JEE examination. For better performance in this section, it is required to keep a check on every topic in this chapter. Hence, it is necessary to give importance to this chapter from JEE's point of view.