## Saturday, 18 August 2012

### CBSE Class 9 - Science - CH10 - Gravitation (Worksheet-1) 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 centre of all celestial bodies was proposed by _____.

2. Heliocentric model was proposed by ______.

3. According to the 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 a 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 ________ Nm2kgs-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 the 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 the 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 centre of the earth, the acceleration due to gravity is _______.

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

Gravitation Important Formulae

1. Ptolemy
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 1024 kg

10. does not vary, different
11. same time
12. independent
13. 9.8 m/s2
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  #### 1 comment:

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