The Concept of Universal Gravitational Force

Rebiaz Studio

Newton's Law of Universal Gravitation states that every particle attracts every other particle in the universe with force directly proportional to the product of the masses and inversely proportional to the square of the distance between them.

Transcript

00:00Hi friends, welcome to the Rebius channel.

00:07In the first series of the Gravitational Physics course, we will discuss Newton's Law of Gravity.

00:15We start from an observation.

00:20This is an illustration of the Earth's surface.

00:26Let's say you climb a ladder to reach a height.

00:29There you put an apple at a point in the air.

00:35The apple will fall towards the Earth's surface.

00:40So do oranges

00:45and melons

00:48or other objects.

00:51All of these objects move straight towards the Earth's surface.

00:57Of course you will ask,

00:59why do these objects move like that?

01:04If you have taken a course on Newton's Laws of Motion,

01:08the object moves because of a force.

01:11Of course the object gets a force.

01:15This force is known as the universal gravitational force.

01:21The magnitude of the force can be formulated as F equals big G big M M over R squared.

01:31The direction of the force is downward or towards the center of the Earth.

01:38To understand this formula, we will show an illustration of the Earth in a smaller size.

01:46So, big M here is the mass of the object that affects another object.

01:53In this case, it is the Earth.

01:57M is the mass that gets the gravitational force

02:01or the mass of the object that is affected by another object.

02:07R is the distance between two objects.

02:11Each object has a center of mass.

02:14The center of mass of the ball is the point at the center of the ball.

02:19Well, R is the distance between the two centers of mass.

02:23So, R is not the distance of the object to the surface of the Earth.

02:28However, R is the distance of the object to the center of the Earth.

02:34Big G is a constant.

02:36Its value is 6.67 times 10 to the power of negative 11 Newton meters squared over kilogram squared.

02:45This constant is also known as the universal gravitational constant.

02:52Before closing this series, we have previously known that the gravitational force is mg.

03:00What is the difference with this equation?

03:05The gravitational force F is equal to mg applies to objects that are affected by the Earth only.

03:11And, the object is near the surface of the Earth.

03:17While F is equal to big G, big M, M over R squared applies to all interactions of objects with mass at any distance.

03:26That is why there is a universal word in the term of this force, universal gravitational force.

03:33We will discuss this further in the next series.

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