Types of the Moment of Force

Force is required for the various activities we perform throughout our lives. Whether it is throwing a ball or moving a bag, every action requires force. In fact, no action can be completed until we exert some form of force. The moment of force is an important concept in physics; it is studied alongside the concept of force. The moment of force refers to the force exerted when a body rotates (is rotational). The moment of force can be classified into three types. These are the mass moment of inertia, the area moment of inertia, and the polar moment of inertia. 

We all have seen a door rotating about its hinges, the blade of a helicopter rotating around the nut, the wheels of a racing car rotating at immense speeds, etc. All these phenomena have one thing in common, Rotational motion. But what causes rotational motion?

The reason behind any change in the state of a body, either putting it into motion after rest or putting it to rest when it is in motion is due to the application of force. Without force, there would be no perceivable change in the physical world. But different types of forces have different types of effects.

Before learning more about these types of the moment of force, it is important to understand what force and the moment of force mean. In this blog, we explain the meaning of force and the moment of force. We will also define and describe the three types of the moment of force—the mass moment of inertia, the area moment of inertia, and the polar moment of inertia.

Force – An Overview

Force is defined as the push and pull between two objects. When one object interacts with another, both exert a pressure called force. Force is present only when two or more objects collide or interact with each other. 

For instance, when you throw a ball on the ground, force is involved. Here, a certain amount of force is exerted by the person throwing the ball. As soon as the ball touches the ground, it interacts with the ground and exerts force. 

Forces can be classified as contact forces or forces as consequences of actions. When objects touch each other, the force exerted is called a contact force. When objects do not actually touch each other but still some kind of force exists between them, such a force is called a force as a consequence of actions. 

Force is essential in any work or innovation we undertake. Force is exerted with every action, from the mining process to building blocks. It has a particular direction and magnitude. When we exert force, it moves in a specific direction. It can change its direction based on the hurdles it encounters. For instance, the force of a river might slow down when it passes through rocky areas or rocks. 

Forces have magnitude. The magnitude refers to the rate at which force is exerted. It can vary depending on the nature of the activity. For instance, in coal mining, the pressure exerted by coal miners has a high magnitude. 

Based on these qualities, force is said to be a vector quantity. As force is a vector quantity, it can be represented through various vector diagrams. Force includes the moments of force, which have been explained below. 

The Moment of Force – An Overview

The moment of force is defined as the turning ability of force. It is a force that rotates a body or an object on a particular axis, end, or point. This moment of force is also called torque, rotational force, or the turning effect. However, force in physics differs from how force is interpreted in mechanics. 

The moment of force refers to the force (applied to a rotational system) using which a body rotates about a definite point. However, this force differs from the force that moves an object. The moment of force rotates a body, and based on the rotation it prompts, it differs from the moment of force that moves an object or a body. Here, the force begins in a manner that causes the object to rotate. The moment of force is seen when there is an absence of equal and opposite forces being applied to an object (from opposite sides). 

For example, if you and your friend are pushing a door from either side of the door, it would create force but not the moment of force. As the force (push) is exerted from both sides, the rotational factor of the moment of force is absent. As long as you both push it, the door will receive equal force. However, if you stop pushing, the only force acting on the door will be the force your friend exerts, which will cause the door to turn and swing open. The door’s movement of swinging open is the moment of force. 

The moment of force is calculated using the formula:

Moment = Force x Moment Arm

M = (F)(d)

Here, 

M= Moment of force

F= Force line

d= Moment arm

The moment of force is the product of force in action and the moment arm. The moment arm is the perpendicular distance between the force and the centre. There are three prominent types of the moment of force. These are the mass moment of inertia, the area moment of inertia, and the polar moment of inertia. 

The Types of the Moment of Force 

The moment of force can be classified into three types. Depending upon inertia which is based on their deflection and resistance to an object and these types of inertia explain below.

• Mass Moment of Inertia: The mass moment of inertia is described as the resistance generated by an object to rotate based on its own mass. Some examples of the mass moment of inertia are ceiling fans, parts of pumping machines, and mechanical devices called flywheels. The mass moment of inertia for such objects is low, thereby reducing the use of electricity. Inertia for such objects is approximately at the axis of rotation.

• Area Moment of Inertia: The area moment of inertia is described as the resistance generated by a body in motion to suppress or deviate. In such cases, inertia is free of mass and depends on the region of the body in motion. The beam is an instance of an area moment of inertia.

• Polar Moment of Inertia: The resistance generated by an object while in force to the torsion is called the polar moment of inertia. The polar moment of inertia varies from the mass moment of inertia. The twisting factor makes it different from the rotating factor. The shaft is a prominent instance of a polar moment of inertia.

Types of moments of force are classified based on their ability to exert force on rotating objects. 

Conclusion 

This post discusses the importance of force. It discusses force in detail, along with the types of forces and the moment of force (the force that rotates a body or an object). The three main types of the moment of force are the mass moment of inertia, the area moment of inertia, and the polar moment of inertia.