Couple Moment and its Application

Consider that you need to turn a valve or a car's steering wheel. You can operate the valve or the steering wheel with two hands by pushing up with one and pulling down with the other. The valve or the steering wheel turns as a result. Your hands should have produced two equal, parallel, but opposing pressures. This pair of forces produces a turning effect and is technically defined as a couple as follows. An uneven force is applied to the element being tightened in addition to the turning moment when a wrench, on the other hand, is operated by force applied at just one end. In this case, the concept of the couple comes into the picture. In this article, we will discuss a couple of moments in detail.

What is the Couple?

An opposing pair of equal parallel forces is referred to as a couple in mechanics. A couple can only influence a body's rotation. When we apply equal forces in a particle then it begins to rotate. We know from Newton’s third law that when a force is applied to a matter then it replies with same amount of force in opposite direction. We can use this law to understand the basic concept of couple. When two equal and opposite directed forces are applied in two positions of a line, two forces cancel the effect of each other. These forces develop a torque. For this torque the matter starts to rotate. From all this discussion we can understand that when two forces with same potential and opposite direction applied in a matter it starts to rotate this is called couple. We can get the value of the torque from the basic formula of torque.

Moment of the Couple

The couple's moment is defined as the sum of one of the two forces in a pair and the angle formed by their lines of action. This quantity is sometimes referred to as the couple's arm. The size of a moment produced by a single force at a point is determined by the force's strength and the point's position. The moment of a couple, on the other hand, is always constant and is only influenced by the strength of the opposing forces and the separation between them. The force plus the angle between the two forces' lines of action is multiplied together mathematically to get the couple's moment. In this context, the term "arm of the couple" refers to the separation between the perpendicular axes of action of two forces. In other words, the moment of force is equal to the applied force times the sum of any two forces' arms.

The simplest sort of couple consists of two equal and opposing forces with diverging routes of activity. The forces produce a torque, which is a turning effect or moment around an axis normal (perpendicular) to the plane of the forces. The couple's torque is measured in newton meter using SI units. The following formula can be used to calculate the torque's magnitude if the two forces are F and -F:

T=Fd

where

T is the couple's moment

F is the force's magnitude.

The angle (moment) between the two parallel forces is d.

The torque's direction is determined by the unit vector, which is perpendicular to the plane containing the two forces and positive for a counterclockwise pair. The torque's magnitude is equal to F • d. The torque is the cross product of d and F when d is considered as a vector between the forces' places of action,

T=|F×d|

Applications of Couple Moment

In the physical sciences and mechanical engineering, couples are crucial. Several applications of couple are:

1. A pair of forces is performed with the fingers to open and close the device's lid.
2. Every time we spew, the tap opens and shuts.
3. One more example of a couple is when the churn starts to rotate while one hand holds the ends of the rope while the other hand moves in the opposite direction.
4. The pencil starts to revolve when both hands are holding it between them, and the palms of each hand are running in opposite directions.
5. When turning a moving bicycle, we use our hands to apply force to the handle.