CBSE Class 9 Gravitation. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

**Chapter−10**

**Gravitation**

**Gravity** is one of the most basic forces in the universe. It plays a fundamental role not only in the structure of our solar system but also in the way objects behave on Earth. In this section, we will talk about gravity on a small scale. We will discuss topics such as weight, free fall, and ballistics. We will learn the physics of phenomena we experience daily and take for granted

**1.Gravitation**

Gravitation is the force of attraction between two objects in the universe. Gravitation may be the attraction of objects by the earth. This force is proportional to the product of masses of the objects and inversely proportional to the square of the distance between them. It is ndependent of medium.

Gravitation force=GMm/r^{2}

Eg :- If a body is dropped from a certain height, it falls downwards due to earth’s gravity. If a body is thrown upwards, it reaches a certain height and then falls downwards due to the earth’s gravity.

• Gravitation may be the attraction between objects in outer space.

Eg :- Attraction between the earth and moon.

Attraction between the sun and planets.

**GRAVITY**

• A natural force that pulls all objects toward the center of the earth

• keeps the moon orbiting

• It holds stars together . . .

• And binds galaxies together for billions of years ….Prevents Planets from lo sing their atmospheres.

**Test yourself:**

1. When we move from the poles to the equator. Hence, the value of g decreases. Why?

2. What is the difference between gravity and gravitation?

2.Universal law of gravitation: - “Inverse square law”- All bits of matter attract all other bits of matter………..

• The universal law of gravitation states that, ‘Every object in the universe attracts every other object with a force which is directly proportional to product of the masses and inversely proportional to the square of the distance between them.’

• The SI unit of G is N m^{2} kg^{-2} and its value is 6.673 x 10^{-11} N m^{2} kg^{-2}

• The strength of the gravitational attraction between two objects depends on two factors:

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