Knowing More About Examples of a Moment

The tendency of a force to create rotation is called the moment of a force. The moment of a force is measured over the axis around which a body rotates. Daily activities like opening a door around a fixed hinge or closing a bottle of water involve the moment of a force. The moment of a force arises when an unopposed force is applied on a body, making it twist. A force applied along a line that does not pass through the centroid of the body will create a twisting motion, resulting in the moment of the force. It is caused by the absence of an opposing force along the line of an applied force. Let us try to understand how a moment of force is applied in real life with a few examples.

A Door Opening Around a Fixed Hinge

The rotational aspect of force causes a moment of force. A daily life example of this is when we open or close a door. The door’s structure is such that it can utilise the moment of the force to its maximum.

Let us analyse the motion of a door opening around fixed hinges to understand how the moment of the force is applied. A door is pushed when a force is applied to the door. This force can be perpendicular to the face of the door or at an angle. There will always be a component of the force that is acting perpendicular to the face of the door.

This perpendicular component is applied at a distance from the hinges. The hinges of the door are fixed and act like pivots in the motion of the door. Therefore, when this force is applied to the door, the force is at a distance from the pivot. Thus, the moment of the applied force results in a circular motion. 

Another important aspect is that the moment of the force is only considered when the applied force has no opposing force applied that is equal to it applied. This means only an unopposed force causes a moment of the force.

Seesaws

A door has only one moment of force acting upon it. But a body can have more than one moment of force acting upon it. An example of this can be seen in the seesaws. The seesaw is a simple device where two weights put on both sides cause the seesaw to oscillate up and down. 

The principle behind this is that the weight of one body causes a certain amount of force on the seesaw. The seesaw is attached to a spring in the centre, which acts as the pivot for the seesaw. When the force by one weight is applied, a moment of the force occurs, causing the seesaw to go downwards.

When one side of the seesaw goes down, the weight on the second side, which moves upwards, also applies a force. This causes the other side to come down and the first side to go up. The result of these two moments of force acting on the seesaw cause it to go in different directions alternatively.

Scissors or a Spanner Turning Around a Nut

When we use scissors, we create two moments of force in opposite directions, making the blades come together. In a scissor, two blades are attached to two handles that are held together by a centre screw piece that acts as the pivot. 

When force is applied to this handle, a moment of the force is caused. Since the force is applied in opposite directions, the moments also act in opposite directions, bringing the blades together.

Trying to turn a nut with bare hands requires a lot of force. But when a spanner is used, the work becomes easier. This is because a spanner adds distance between the force and the pivot, i.e., the nut. 

When this distance is added, a moment of the force is generated. This causes the nut to rotate and unscrew easily. The distance created by the spanner allows for more moments to be generated for the same amount of force.

Conclusion

Moment of force is the phenomenon that occurs when a twisting force is applied to a body. It is measured as the tendency of a body to twist along a given axis. Applying force to create rotation is the basic principle in many objects like planes, submarines, doors, etc.  

The most popular examples of the moment of force in real life are the opening and closing of a door along a fixed hinge, a seesaw, and unscrewing a nut with a spanner. When force is applied to a door, the hinge acts as a pivot. The generated moment of a force turns the door. In a seesaw, two moments of force act at two different points to generate the seesaw motion. 

For a pair of scissors, a couple is created by the two moments of force acting in different directions, causing the scissor blades to come together and cut the object. A spanner adds distance between the nut and the force, allowing for a moment to be created that unscrews the nut.