Application of parallel forces in the rotation of an object

Introduction

Objects often move when a force is applied to them. For example, a car will continue to remain in a state of rest until a force from the engine applied to the tires causes it to start moving. In this case, the engine produces that single force that causes the vehicle to move forward. On the other hand, certain objects move as a result of the action of more than one force. At times, the forces applied might move in the same direction. There are times however, when two or more forces applied in opposite directions cause the object to move.

In this discussion, we will talk about couples - not of people that are married, but two forces acting on an object. We will understand how the application of couples are used to achieve the movement of an object. This discussion will also include some real-world examples of how such couples are used to achieve the movement of objects.

Couple as an example of a parallel force

In order to understand how certain objects move, it is important to grasp the parallel forces. Two forces can exert their effect on an object at the same time, causing the object to move or rotate. If that happens, those two forces are said to be a parallel force. Sometimes, the two forces might be acting on the same direction. At other times though, the parallel forces might be acting in the opposite direction. When two forces act on the same object but in opposite directions, then such forces are referred to as a Couple.

Couples are very important in the movement of certain objects. One important thing to note is that just like other parallel forces, couples can never meet. While the effects of their action on an object can cause the object to move, the lines of action of the two forces can never intersect.

Most times, forces in a couple can only affect the rotational movement of an object and not a linear direction of movement. The direction of application of such forces often follow the path of a round circle. It is important to note that for two forces to be truly considered a couple, they must also have the same magnitude and not acting in a straight line. Being equal in magnitude, the strength of one of the forces acting in one direction must be equal to that of the second force in the other direction. In this way, they are able to cancel each other out and cause the object to rotate uniformly.

Illustrating a Couple - Wheel and Tap

The above illustration helps us to see how couples act and their effect. In the image above, there is a round object experiencing the effect of two parallel forces known as a couple. The first force labelled A is acting towards the top direction, attempting to move the object in the process. Another force labelled B is acting downwards at the same time, attempting to push the object in that direction too. If these two forces act at the same time with equal magnitudes, the object will start to rotate uniformly.

So here are real-world examples of a couple in cation:

• A steering Wheel: Notice that when a person is driving a car, they turn the steering wheel in order to move the vehicle in a desired direction. A steering wheel was designed to be handled with two hands. The two hands must produce a turning force in a certain way to turn the steering.

One of the hands pulls the steering wheel in one direction while the other hand pulls it in the opposite direction. The driver ensures that the pressure or forces exerted by the two hands in opposite directions are equal. Thus, the couple - two forces of equal magnitude acting in opposite directions - cause the steering wheel to turn.

Here is another application of couples:

• A water tap: Have you ever tried to turn a water tap on? That is another example of a couple. You split the fingers into two. The first group pushes the tap in one direction. The other group pushes it in an opposite direction. If the forces applied are uniform and opposite, you can turn the tap on or off depending on what you wish to do.

Importance of Couples

As shown in the above examples, couples are important in achieving any form of rotational motion especially in wheels and other round objects. They make it easier to do the work with the two forces of equal magnitude acting in parallel.

When driving a car for example, which is easier: to turn the steering wheel with one hand or the two hands? With one hand, only a single force is applied in one direction. It becomes more difficult to turn the car. In fact, if the vehicle is a heavy duty one, its almost impossible to handle it with just one hand. The two hands produces a couple of parallel forces that makes it efficient to do the work. The same is through when turning a tap on. Its harder when pushing the tap in one direction with the whole fingers. Its far better to split the fingers and apply two forces in different directions.