All of us have heard about gravity. A ball thrown up in the air ultimately descends to the ground, a person who jumps off a clip falls downwards, and a ripe apple falls on the ground when the tree is shaken; all of these and many more are common examples of gravity. From these examples, we can deduce that gravity is a factor that pulls anything toward the Earth.
From intuition, any push or pull acting on an object that displaces or tries to displace the object is called force. So, we can build up a basic idea that gravity is a force that pulls anything toward the Earth. The idea is not complete and we will add to it as we proceed in this chapter. Gravitation is nothing but an umbrella term for gravity. Hence, we will discuss Gravitation ahead of gravity in this unit.
Gravitation
As understood earlier, gravitation is a force. In fact, it is one of the four fundamental forces existing in nature, alongside Strong force, Weak force, and Electromagnetic force. Recall the examples of gravity discussed above; in none of the conditions, the objects were touching the ground: they were in the air. Regardless, the objects were being pulled by gravity.
A point to note down, unlike most of the forces we have discussed so far, the force of gravitation does not require two objects to be in physical contact, therefore, gravitation is also called non-contact force. If you are wondering, what is gravitation force actually, because I have not defined it yet, we need to recall a final concept before we define it. Newton's third law describes the effect of force and states the action-reaction pair exists for all forces. So, when the Earth attracts (we replaced the word pull with attract) an apple to itself, the apple must also attract the Earth toward itself. Now, we are in a state to define the gravitation force.
“Gravitation is an attractive force with which an object attracts another object toward itself.”
There is much to add to the definition quoted above. To do so, we will have to look into Newton's Universal Law of Gravitation who studied the gravitational force and drew some major conclusions in the following chapters.