# CBSE Class 9 Science, Gravitation: Important topics and questions

**Below are given some important term/topics to revise from chapter- Gravitation:**

- Definition and nature of gravitational force
- How weight of a body varies place to place
- What is the application of centripetal force?
- Think about the nature of motion path of moon in absence of centripetal force
- Universal law of gravitation and universal gravitation constant
- Unit and value of universal gravitation constant
- Importance of universal gravitation constant
- Universal law of gravitation is applicable for light bodies or for heavy bodies
- Difference between mass and weight
- A man has a mass of 60 kg on earth. What will be the mass of man on moon(g
_{m}=g_{e}/6) - Kepler law and its application. Numerical based on kepler law
- SI unit of weight and force
- Difference between thrust and pressure. Unit of thrust and pressure
- The mass of the earth is 6 x 10
^{24}kg and that of the moon is 7.4 x 10^{22}kg .If the distance between the earth and moon is 3.84 x 10^{5}km. Calculate the force exerted by the earth on the moon. [ G= 6.7 x 10^{-11}N m^{2}kg^{-2 }] - Concept of free fall motion
- Use of all the three equations of motion by putting “g” in place “a”
- An object is thrown vertically upwards and rises to a height of 10 m. Calculate (i) the velocity with which the object was thrown upwards and (ii) the time taken by the object to reach the highest point
- Concept of buoyancy
- Why does an object float or sink when placed on the surface of water?
- Archimedes’ principle and concept of density
- Formula of relative density
- Relative density of silver is10.8. The density of water is10
^{3}kg m^{-3}.What is the density of silver in SI unit?

**Important Questions are as below:**

**Q.** What happens to the force between two objects, if

(i) the mass of one object is doubled?

(ii) the distance between the objects is doubled and tripled?

(iii) the masses of both objects are doubled?

**Q.** Why will a sheet of paper fall slower than one that is crumpled into a ball?

**Q.** Why is G called universal constant?

**Q.** Does law of gravitation obey newton’s third law?

**Q.** Establish the relation between G and g?

**Q.** what is the difference between weight and mass?

**If you have any Question/Point on the above information, please ask/discuss it in the** **CBSE Group**