Question

NCERT notes of class 9th physics chapter 3 gravitation​

Answer 1

• The chapter Gravitation of class 9th of NCERT is easy.
• In chapter there is:

1. Introduction to Gravitation
2. What is Gravitation: Gravitation or just gravity is the force of attraction between any two bodies. All the objects in the universe attract each other with a certain amount of force, but in most cases, the force is too weak to be observed due to the very large distance of separation.
3. Types of forces: Gravitational force, Electromagnetic force, Strong nuclear force, Weak nuclear force.
4. Gravitational force: Gravitational force is the weakest force out of the four forces.
5. Electromagnetic force: The electromagnetic force is a type of physical interaction that occurs between electrically charged particles.
6. Strong Nuclear force: The strong force holds together quarks, the fundamental particles that make up the protons and neutrons of the atomic nucleus, and further holds together protons and neutrons to form atomic nuclei.
7. Weak nuclear force: Weak force is the force existing between the elementary particles which are responsible for certain processes to take place at a low probability.
8. The universal law of Gravitation
9. Acceleration due to gravity
10. The moon's falling- moons revolution around earth
11. Centripetal force:
12. Free fall and motion:  when an object in under free fall, acceleration due to gravity is constant.
13. Weight and mass: Weight is nothing but a force of attraction of the Earth on an object.
14. Thrust and pressure: force acting on an object perpendicular to the surface is called thrust.
15. Pressure in fluids
16. Relative density: Relative density= density of a substance/ density of water
17. Kepler's law: Kepler's first law- the law of orbits, Kepler's second law- the law of equal areas, Kepler's third law- the law of periods.

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