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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) 1st
b) 2nd
c) 3rd ✓
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 vc = ______.
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 1st 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) gRE2 / G ✓
b) gG / RE2
c) gG / RE
d) gRE / 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) √ gME
(c) √ g(R + h)
(d) √ gGR
FILL IN THE BLANKS:
- Gravity’ is taken from Latin word ‘gravitas’ means ‘weight’.
- The gravitational force (pull) of Earth is known as gravity.
-
Everybody in the universe attracts every other body with a gravitational force of magnitude:
F = Gm1m2/ r2 - Gravitational force forms an action-reaction pair.
- Newton's law of gravitation is consistent with Newton's third law of motion.
- “G” has constant value through out the universe.
- “g” has different values at different places.
- A gravitational field is a region in which a mass is attracted due to gravitational attraction.
- Weight of an object is the gravitational pull of Earth acting on it.
- W = mg.
- Mass of Earth is 6.0 x 1024kg.
- A satellite is an object that revolves around a planet.
- Natural satellite is a planet that revolves around another planet naturally.
- Moon is natural satellite of Earth.
- An artificial satellite is an object which is sent to space to revolve around a planet.
- Sputnik-1 and Explorer-1 are artificial satellites.
- Meteosat are artificial satellites of Earth.
- Critical velocity is the constant horizontal velocity needed to put a satellite into an stable circular orbit around the Earth.
- “G” is also known as Newtonian constant of gravitation or the Cavendish gravitational constant.
- The gravitational field strength “g” is approximately 10 Newton per kilogram or 10 Nkg-1.
- An object of mass 1 kg has a weight of 9.8 N near the surface of Earth.
- 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”.
- Ocean tides are caused by the gravity of Sun and Moon.
- The Earth has 9.3 times more mass than Mars.
- Earth is used for communication purpose, therefore it is known as “Communication Satellite”.
- Velocity of Geostationary satellite with respect to Earth is zero.
- 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 |
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