Force and Motion

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Define what is Motion and Force?

There are different types of motion related to the human body. Do you know what causes and obstructs motion in the body or object? The answer is the application of force. In general physics, the term force and motion are interrelated and are two sides of the same coin. For example, the interdependence of force and motion can be viewed from the perspective of throwing a ball and catching it back. A force causes interaction between two or more bodies and when that remains unobstructed generates a change in the state of motion. To figure out this relationship existing between force and motion we have to understand the terms individually. 

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What is Force? 

To comprehend what is force, we have to think in terms of pull and push. The push and pull acting on an object or energy as a movement or attribute of physical activity is defined as forced. 

Similiar to push and pull, words like squeeze and stretch also explains the concept of what forces can do. This mainly happens when two entities come in contact. Based on Newton’s universal law of gravitation every object in this universe exerts a force on other objects.  


What is the S.I. unit of Force?

If you want to know what is the S.I. unit of force, we have to know about Sir Issac Newton who first studied gravity and force. So, it is obvious what is the unit of force. It is called the Newton.

F = ma

1 Newton = 1 kg x 1 m/s2


What is Force measured in? 

These are the units of force which explains what is force measured in. 

  • This is a standard international system of a unit (SI unit) which is expressed in Newton (N).

  • There is a centimetre gram second system of a unit (CGS unit) which is expressed in dyne.

  • There are other units like pound-force, kip, poundal, kilopound. 


What is normal Force? 

The support force exerted upon an object that is in contact with a stable object describes what is normal force. For example, an object is put on the table and the table is exerting an upward force upon the object to support its weight. There are times when a normal force is exerted horizontally when two things are in touch with each other. 


What is Motion?

We can define what is motion in simple words regarding the change of position of the body to time. A train moving, water flowing from the tap, boy walking, etc., all exhibits the state of motion. The act of breathing is also defined as motion. Therefore, every physical process that we experience in this universe is composed of some or other sort of motion. Neither a motion can be swift, nor it can be slow. All this explains what is the meaning of motion. It is vital to understand the concept of motion because it has relevance in the physical world. 


What is the meaning of Motion?

Various terms help us to describe further what is motion in the actual sense. It includes distance, displacement, time and speed. With terms like displacement and distance, we can describe a change in position. Distance is not easy to explain since it depends upon the path that one has taken. On the contrary, displacement is an easier concept because it always gives a definite answer. It is the shortest distance covered between the two points. If the motion is in the straight line, distance and displacement will be the same. If the motion is not in a straight line, the distance always tends to be greater than the displacement. 


The Relation Between Force and Motion

Force and motion are deeply interconnected with each other. What force can do is produce motion in an object or body. For instance, an object is moving and we can say that a force is acting or must have been acted upon to cause the state of motion. When force is applied, it changes the position of the object concerning time resulting in motion. The motion, in other words, is described as a change in speed or change in direction. Isaac Newton was the first to discover the relation between force and motion. He came to three conclusions: 

  • Force can accelerate the object. 

  • Force can decelerate the object. 

  • Force can cause a change in the direction of the object. 


Did You Know?

Force has a different effect on the object or body. These are listed below:

  • Force application can make a body at rest to move.

  • Force can accelerate or decelerate the speed of a moving body.

  • Force can completely stop a moving body.

  • Force can also change the direction of a moving body

  • Force can transform the shape and size of a body. 

FAQ (Frequently Asked Questions)

Q1: How can Force cause a body to accelerate or decelerate?

Ans: When an object or body is in rest and a force is applied, it starts to move until and unless it is acted upon by an opposing force. When you throw the shuttlecock towards the opponent while playing badminton, the shuttle begins to move forward from its initial position of rest towards the other end. From the initial position of rest, when something starts to move forward it accelerates. This acceleration is a positive change in the velocity over a time period. On the other hand, if force is implemented to the opposite direction of a moving object, it will decelerate or slow down and finally stop altogether if the application of force is continued. For example, when a goalkeeper stops a football, he makes it to decelerate and stop.

Q2: What are the types of Motion?

Ans: The different objects move in different ways, some moves through a straight line, some in a curved path while others in a different way. Based on the nature of the movement, motion can be categorized in three ways: Linear Motion, Rotary Motion and Oscillatory Motion. In linear motion, the object moves from one point to the other in a straight line or a curved path. For example, the motion of vehicles, football, and others. Rotatory motion is the motion that happens when a body rotates on its own axis. A classic example is the motion of the earth. Oscillatory motion is where the body moves about its mean position like guitar strings, pendulum, swings, etc.