Gravitation - Physics For Class IX (Science Group) - Multiple Choice Questions (MCQs) , Fill in the blanks and Concept Map

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Physics For Class IX (Science Group)
UNIT 6: GRAVITATION
Multiple Choice Question

Section (A) Multiple Choice Questions (MCQs)

Tick mark (✓) the correct answer:
1. The motion of a falling ball towards Earth is due to the _____.
a) Weightlessness
b) Gravitational force ✓
c) Acceleration due to gravity
d) Both 'a' and 'b’

2. Newton's law of gravitation holds between every two objects on the _____.
a) on Earth
b) on Jupiter
c) on Moon
d) on Universe ✓

3. Numerical value of G is ______.
a) G = 6.673 10^-11 Nm² kg^-2 ✓
b) G = 6.673 10¹¹ Nm² kg^-2
c) G = 6.763 10^-11 Nm² kg^-2
d) G = 6.763 10¹¹ Nm² kg^-2

4. Gravitational field of Earth is directed _____.
a) towards the Earth ✓
b) towards the Sun
c) towards the Moon
d) away from Earth

5. ______ was the first scientist who gave the concept of gravitation.
a) Einstein
b) Newton ✓
c) Faraday
d) Maxwell

6. According to Newton's law of universal gravitation force ∝ _______.
a) m₁ m₂
b) ¹/_r²
c) r²
d) Both (a) and (b) ✓

7. Gravitational force is always ______.
a) Repulsive
b) Attractive ✓
c) Both
d) None of these

8.Numerical value of ______ remains constant every where.
a) g
b) G ✓
c) F
d) W

9. Gravitation force is ______ of the medium between the objects.
a) Dependent
b) Independent ✓
c) Both 'a' and 'b'
d) None of these

10. Near Earth's surface g = ______.
a) 10 ms^-2 ✓
b) 1.6 ms^-1
c) Both (a) and (b)
d) None of these

11. Newton's law of gravitation is consistent with Newton's _________ law of motion.
a) 1^st
b) 2^nd
c) 3^rd ✓
d) All of them

12. Spring balance is used to measure _________.
a) Mass
b) Weight ✓
c) Elasticity
d) Density

13. Your weight as measured on Earth will be _____.
a) Increased
b) Decreased ✓
c) Remains same
d) None of these

14. Mass of Earth is _____.
a) 6.0 x 10²³ kg
b) 6.0 x 10²⁴ kg ✓
c) 6.0 ´ 10²⁵ kg
d) 6.0 ´ 10²⁶ kg

15. _____ is a natural satellite.
a) Earth
b) Jupiter
c) Moon ✓
d) Mars

16. A communication satellite completes its one revolution around the Earth in ______ hours.
a) 6
b) 12
c) 18
d) 24 ✓

17. The velocity of a satellite is _____ of its mass.
a) Independent ✓
b) Dependent
c) Equal
d) Double

18. _______ are used to put satellites into orbits.
a) Helicopter
b) Aeroplane
c) Rocket ✓
d) None of these

19. The critical velocity v_c = ______.
a) gR
b) ^g/_R
c) √ gR ✓
d) √ ^g/_R

20. According to Newton's law of universal gravitation, force is inversely proportional to ____.
a) m₁ m₂
b) ¹/_r²
c) r² ✓
d) Both (a) & (b)

21. According to Newton's law of universal gravitation, force ∝ to _____.
a) m₁ m₂ ✓
b) ¹/_{m1 m2}
c) r²
d) Both (a) & (c)

22. It changes the path of the Moon around the Earth.
a) centripetal force
b) centrifugal force
c) pull of the gravity ✓
d) turning effect of the force

23. It determines the gravitational force acting per unit mass:
a) G
b) g ✓
c) 𝜏
d) None of these

24. Gravitational force is always present between two objects because of their:
a) volumes
b) shapes
c) density
d) masses ✓

25. Gravitation force follows the:
a) direct square law
b) inverse square law ✓
c), direct law
d) inverse law

26. In 1798, he completed the 1^st experiment that demonstrated Newton's Law of universal gravitation.
a) Einstein
b) Cavendish ✓
c) Faraday
d) Maxwell

27. Earth's field force is a:
a) non-contact force ✓
b) contact force
c) Both 'a' & 'b'
d) None of these

28. Weight is measure in:
a) kg
b) kg-m
c) ^kg/_m
d) N ✓

29. Ocean tides are caused by the:
a) gravity of the earth
b) gravity of the sun
c) gravity of the moon
d) Both "b" & "c" ✓

30. The first artificial satellite, Sputnik-1, was sent into space by:
a) USA
b) USSR ✓
c) UK
d) China

31. The gravitational pull of the Earth on the satellite provides the needed to keep a satellite in orbit around some planet.
a) centripetal force ✓
b) centrifugal force
c) gravity
d) force of attraction

32. The height of a geostationary satellite is about ____ km from the surface of the Earth.
a) 32,000
b) 35,600
c) 40,800
d) 42,300 ✓

33. The time required for a satellite or complete one revolution around the Earth in its orbit is called its:
a) period
b) rotational period
c) time period ✓
d) revolving time

34. Expression for the mass of the Earth is:
a) ^gR_E2 / _G ✓
b) ^gG / _RE²
c) ^gG / _RE
d) ^gR_E / _G

35. The velocity that a satellite must possess when orbiting around the Earth in an orbit of radius (r = R + h) is:
a) √ R + h / GM
b) √ M(R + h) / G
c) √ G(R + h) / M
d) √ GM / R + h ✓

36. The expression for the time period of a satellite orbiting around the Earth is:
a) 2π √ r/GM
b) 2π √ r²/G²M
c) 2π √ r²/GM ✓
d) 2π √ r²/GM²

37. Sun's gravitational attraction to the Earth is ____ times greater than that of the moon to the Earth.
a) 100
b) 156
c) 177 ✓
d) 189

38. The constant horizontal velocity required to put the satellite into a stable circular orbit around the Earth is called:
a) orbital velocity
b) critical velocity ✓
c) centripetal velocity
d) centrifugal velocity

39. Expression for critical velocity is:
a) √ gR ✓
b) √ gM_E
(c) √ g(R + h)
(d) √ gGR

FILL IN THE BLANKS:

1. Gravity’ is taken from Latin word ‘gravitas’ means ‘weight’.
2. The gravitational force (pull) of Earth is known as gravity.
3. Everybody in the universe attracts every other body with a gravitational force of magnitude:
   F = ^Gm₁m₂/ _r²
4. Gravitational force forms an action-reaction pair.
5. Newton's law of gravitation is consistent with Newton's third law of motion.
6. “G” has constant value through out the universe.
7. “g” has different values at different places.
8. A gravitational field is a region in which a mass is attracted due to gravitational attraction.
9. Weight of an object is the gravitational pull of Earth acting on it.
10. W = mg.
11. Mass of Earth is 6.0 x 10²⁴kg.
12. A satellite is an object that revolves around a planet.
13. Natural satellite is a planet that revolves around another planet naturally.
14. Moon is natural satellite of Earth.
15. An artificial satellite is an object which is sent to space to revolve around a planet.
16. Sputnik-1 and Explorer-1 are artificial satellites.
17. Meteosat are artificial satellites of Earth.
18. Critical velocity is the constant horizontal velocity needed to put a satellite into an stable circular orbit around the Earth.
19. “G” is also known as Newtonian constant of gravitation or the Cavendish gravitational constant.
20. The gravitational field strength “g” is approximately 10 Newton per kilogram or 10 Nkg^-1.
21. An object of mass 1 kg has a weight of 9.8 N near the surface of Earth.
22. British scientist George Atwood (1746-1807) used two masses suspended from a fixed pulley, to study the motion and measure the value of ‘g’. This is named as “Atwood Machine”.
23. Ocean tides are caused by the gravity of Sun and Moon.
24. The Earth has 9.3 times more mass than Mars.
25. Earth is used for communication purpose, therefore it is known as “Communication Satellite”.
26. Velocity of Geostationary satellite with respect to Earth is zero.
27. The velocity required to keep the satellite into its orbit is called “Orbital Velocity”.

CONCEPT MAP

Acceleration due to gravity “g” at different planets

Planet	Value of g ms-2
Earth	10
Moon	1.62
Venus	8.87
Mars	3.77
Jupiter	25.95
Sun	274
Mercury	3.59
Saturn	11.08
Uranus	10.67
Neptune	14.07

Mass and Radius of different planets.

Planet / Star	Mass (Kg)	Radius (m)
Sun	1.99 x 1030	6.96 x 108
Moon	7.35 x 1022	1.74 x 106
Mercury	3.30 x 1023	2.44 x 106
Venus	4.87 x 1024	6.05 x 106
Earth	5.97 x 1024	6.38 x 106
Mars	6.42 x 1023	3.40 x 106
Jupiter	1.90 x 1027	6.91 x 107
Saturn	5.68 x 1026	6.03 x 107
Uranus	8.68 x 1025	2.56 x 107
Neptune	1.02 x 1026	2.48 x 107