Nicolaus Copernicus - His theory was one the trigger point for scientific revolution. (credits:wikipedia) |

**Gravitation****(Worksheet-1)**

**Fill in the Blanks**

*1*. Geocentric model i.e. the Earth is the orbital center of all celestial bodies was proposed by _____.

*2*. Heliocentric model was proposed by ______.

*3*. According to Heliocentric theory the _____ is at centre and _______ move around it.

*4*. ______ stated that every planet moves around the sun in closed elliptical orbit, with the ___ at one focus .

*5*. The force which keeps the object moving in a circular path is called _____ force. It always acts towards the _____.

*6*. The force of attraction between two objects is ______ proportional to the product of their masses and _____ proportional to the square of distance between them.

*7*. Kepler's Law of ______ states that a line that connects a planet to the Sun sweeps out equal ______ in the plane of the planet's orbit in _____time intervals.

*8*. The value of Universal Gravitation constant (G) is ________ Nm

^{2}kgs

^{-2}.

*9*. The mass of the earth is ________ kg.

*10*. The mass of an object _____ (varies/does not vary) on the earth as well as on the moon. But its weight is ______(same/different) on both places.

*11*. When objects of different masses and sizes are dropped from same height would reach ground at ______ (same time/different times), considering negligible air resistance.

*12*. Acceleration due to gravity (g) is _______ (dependent/independent) of mass.

*13*. The value of

**g**on the earth's surface is ______.

*14*. The value of

**g**at poles is ______ (lower/higher) than its value at equator.

*15*. The value of

**g**________ (increases/decreases) as we go upwards from the earth's surface.

*16*. The value of

**g**________ (increases/decreases) as we go downwards from the earth's surface.

*17*. The SI unit of weight is _____.

*18*. Weight of an object is the product of ______ and ________.

*19*. At the center of the earth, acceleration due to gravity is _______.

*20*. The value of G was found out by _______ by using a ________.

**Gravitation Important Formulae**

**Answers:**

2. Copernicus

3. sun, planets

4. Kepler's Law of Orbits, Sun

5. Centripetal, centre

6. directly, inversely

7. Law of Areas, areas, equal

8. 6.67 × 10

^{-11}

9. 6. x 10

^{24}kg

10. does not vary, different

11. same time

12. independent

13. 9.8 m/s

^{2}

14. higher

15. decreases

16. decreases

17. Newton (N)

18. mass of the object(m), acceleration due to gravity(g)

19. zero.

20. Henry Cavendish, sensitive balance

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