# Class 9 Physics Chapter 5

Updated: 21 Oct 2023

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Class 9 Physics Chapter 5 is about “Gravitation”. This article includes topics such as Gravitation, Law of Universal Gravitation, Newton’s Third Law of Motion and Universal Gravitation, Mass of Earth, Gravitational Field (Gravity is a field force, Gravitational field strength (free-fall acceleration) ‘g’, Weight changes with location), Variation of ‘g’ with Altitude, Motion of Artificial Satellites (Speed in Circular Orbit Calculation)

## Class 9 Physics Chapter 5 Notes

### Gravitation Notes

Class 9 Physics Chapter 5 Notes

### Class 9 Physics Chapter 5 SLO Notes

Class 9 Physics Chapter 5 SLO Notes

## Class 9 Physics Chapter 5 MCQs

### Law of Universal Gravitation

1 Which scientist formulated the Law of Universal Gravitation?
(a) Albert Einstein
(b) Galileo Galilei
(c) Isaac Newton
(d) Johannes Kepler

Isaac Newton

2 According to the Law of Universal Gravitation, the force between two masses is directly proportional to:
(a) The product of their masses
(b) The square of the distance between them
(c) The cube of the distance between them
(d) The sum of their masses

The product of their masses

3 According to the Law of Universal Gravitation, the force between two masses is inversely proportional to:
(a) The product of their masses
(b) The square of the distance between them
(c) The cube of the distance between them
(d) The sum of their masses

The square of the distance between them

4 If the distance between two masses is doubled, the gravitational force between them will become:
(a) One-fourth
(b) One-third
(c) Half
(d) One-eighth

One-fourth

5 If the mass of the one object is doubled, the gravitational force between them will become:
(a) One-third
(b) Double
(c) Half
(d) One-eighth

Double

6 If the mass of the both objects are doubled, the gravitational force between them will become:
(a) One-fourth
(b) One-third
(c) Four-times
(d) One-eighth

Four-times

7 If the distance between two masses is half, the gravitational force between them will become:
(a) Four-times
(b) One-third
(c) Half
(d) One-eighth

Four-times

8 What law states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them?
(a) Newton’s First Law of Motion
(b) Newton’s Second Law of Motion
(c) Newton’s Third Law of Motion
(d) Law of Universal Gravitation

Law of Universal Gravitation

9 If the distance between two masses is tripled, the gravitational force between them becomes:
(a) One-sixth
(b) One-ninth
(c) One-third
(d) One-twelfth

One-ninth

10 Which of the following quantities has the SI unit “Newton”?
(a) Mass
(b) Weight
(c) Gravitational field strength
(d) Orbital velocity

Weight

11 The gravitational force between two masses will decrease if:
(a) Their masses decrease and the distance between them decreases
(b) Their masses increase and the distance between them decreases
(c) Their masses decrease and the distance between them increases
(d) Their masses increase and the distance between them increases

Their masses decrease and the distance between them increases

12 What is the gravitational force between two objects with masses of 5 kg \ and \ 10 kg , respectively, if they are 2 \ meters apart?
(a) 0.25 N
(b) 83.37 \times 10^{-11} N
(c) 1.00 N
(d) 2.00 N

83.37 \times 10^{-11} N

13 What happens to the gravitational force between two masses if the distance between them is doubled and both masses are also doubled?
(a) It becomes one-fourth
(b) It becomes half
(c) It remains the same
(d) It becomes twice as strong

It remains the same

14 Gravitational constant is represented by,
(a) G
(b) g
(c) K
(d) GC

G

15 The value of gravitational constant G is,
(a) 6.3 \times 10^{-12} Nm^2/kg^2
(b) 9.8 m/s^2
(c) 5 \times 10^{-15} Nm^2/kg^2
(d) 6.67 \times 10^{-11} Nm^2/kg^2

6.67 \times 10^{-11} Nm^2/kg^2

16 The unit of gravitational constant G is,
(a) Nm^2/kg^3
(b) Nm^2/kg^2
(c) Nm^{-2}/kg^2
(d) All \ of \ these

Nm^2/kg^2

17 The value of gravitational constant G does not depend on,
(a) Vacuum
(b) Air
(c) Water
(d) All of these

All of these

18 What will be the value of G if mass of the earth becomes four times:
(a) No change
(b) Four times
(c) One fourth
(d) Doubled

No change

### Newton’s Third Law of Motion and Universal Gravitation

19 Which law states that for every action, there is an equal and opposite reaction?
(a) Newton’s First Law of Motion
(b) Newton’s Second Law of Motion
(c) Newton’s Third Law of Motion
(d) Law of Inertia

Newton’s Third Law of Motion

20 According to Newton’s third law of motion, if object A exerts a force on object B, then object B exerts a force on object A that is:
(a) Twice as large
(b) Half as large
(c) Equal in magnitude and opposite in direction
(d) Unrelated to the force exerted by A

Equal in magnitude and opposite in direction

### Mass of Earth

21 The mass of Earth is approximately:
(a) 6 \times 10^{24} kg
(b) 6.4 \times 10^6 kg
(c) 6 \times 10^{10} kg
(d) 9.8 kg

6 \times 10^{24} kg

22 The mass of earth is symbolically represented by,
(a) M_R
(b) m_E
(c) M
(d) m

m_E

23 The mass of earth is primarily responsible for,
(a) The Earth’s rotation
(b) The Earth’s magnetic field
(c) The Earth’s gravity
(d) None of these

The Earth’s gravity

24 The mass of Earth is determined by using which scientific principle,
(a) Newton’s law of universal gravitation
(b) Law of conservation of mass
(c) Law of conservation of energy
(d) All of these

Newton’s law of universal gravitation

### Gravitational Field

#### Variation of ‘g’ with Altitude

25 What term describes the region around an object in which another object experiences a gravitational force?
(a) Gravitational Pull
(b) Gravitational Field
(d) Gravitational Force Zone

Gravitational Field

26 …………….. is defined as the gravitational force experienced by a unit mass placed in a gravitational field.
(a) Gravitational force
(b) Mass of earth
(c) Gravitational field strength
(d) None of these

Gravitational field strength

27 Gravitational field strength is measured in:
(a) Joule
(b) Meter per second squared
(c) Kilogram
(d) Newton

Meter per second squared

28 “N/kg” is the unit of,
(a) Gravitational force
(b) Mass of earth
(c) Gravitational field strength
(d) None of these

Gravitational field strength

29 The acceleration experienced by an object in free fall near the surface of the Earth is approximately:
(a) 1 m/s^2
(b) 5 m/s^2
(c) 15 m/s^2
(d) 9.8 m/s^2

9.8 m/s^2

30 How does the weight of an object change as its location changes from the surface of the Earth to a higher altitude?
(a) Increases
(b) Decreases
(c) Remains constant
(d) Becomes zero

Decreases

31 What happens to the value of "g" , as altitude increases?
(a) It decreases
(b) It increases
(c) It remains the same
(d) It becomes zero

It decreases

32 An object in free fall experiences:
(a) No acceleration
(b) Constant velocity
(c) Increasing velocity
(d) Constant acceleration

Constant acceleration

33 How does the weight of an object change when taken to a location where the gravitational field strength is greater?
(a) Increases
(b) Decreases
(c) Remains constant
(d) Becomes zero

Increases

34 Which of the following statements about gravitational force is true?
(a) It can only attract, not repel
(b) It can only repel, not attract
(c) It can both attract and repel
(d) It doesn’t exist

It can only attract, not repel

35 The acceleration due to gravity on the Moon’s surface is about one-sixth of that on Earth. If an object weighs 60 N on Earth, what would it weigh on the Moon?
(a) 6 N
(b) 10 N
(c) 60 N
(d) 360 N

10 N

36 Which of the following has the greatest effect on the strength of the gravitational force between two objects?
(a) Mass of one object
(b) Mass of the other object
(c) Distance between the objects
(d) Location of the objects

Distance between the objects

37 Which of the following statements about gravitational field strength is correct?
(a) It is a vector quantity
(b) It is a scalar quantity
(c) It is measured in joules
(d) It is equal to the weight of an object

It is a vector quantity

38 If an object weighs 100 N on the surface of the Earth, what will be its weight when placed at a location where the acceleration due to gravity is half of Earth’s?
(a) 25 N
(b) 50 N
(c) 100 N
(d) 200 N

50 N

39 What is the approximate acceleration due to gravity on the surface of Mars?
(a) 3.7 m/s^2
(b) 9.8 m/s^2
(c) 5.7 m/s^2
(d) 1.6 m/s^2

3.7 m/s^2

40 What is the approximate acceleration due to gravity on the surface of Moon?
(a) 3.7 m/s^2
(b) 9.8 m/s^2
(c) 5.7 m/s^2
(d) 1.6 m/s^2

1.6 m/s^2

41 The radius of Earth is approximately,
(a) 6 \times 10^{24} m
(b) 6.4 \times 10^6 m
(c) 6 \times 10^{10} m
(d) 9.8 m

6.4 \times 10^6 m

42 The radius of Earth is repented by,
(a) r_E
(b) r
(c) R
(d) E

r_E

43 A rocket is fired vertically upward from the surface of a planet. As it rises, its weight will:
(a) Increase
(b) Decrease
(c) Remain constant
(d) Become zero

Decrease

44 What is the force of gravity acting on a 10 kg object on Earth’s surface?
(a) 10 N
(b) 50 N
(c) 98 N
(d) 150 N

98 N

45 The acceleration due to gravity at the surface of a planet is 4 m/s^2 . What is the weight of a 50 kg object on this planet’s surface?
(a) 10 N
(b) 50 N
(c) 100 N
(d) 200 N

200 N

46 An object is dropped from a certain height above the Earth’s surface. As it falls, its speed:
(a) Increase
(b) Decrease
(c) Remain constant
(d) Become zero

Increase

47 What is not true about g?
(a) g is different at different places
(b) g is greater at poles
(c) g is less at poles
(d) g decrease as go higher

g is less at poles

48 If weight of an object on the surface of earth is W. Its weight on the surface of moon will be:
(a) 6W
(b) \frac{W}{6}

(c) \frac{W}{4}

(d) \frac{W}{8}

\frac{W}{6}

49 If mass of both the bodies is 1kg and distance between their centers is 1 m then the gravitational force will be equal to:
(a) G
(b) g
(c) M
(d) m

G

50 When an object is at a height equal to radius of earth above the surface of the earth. What is the value of g ?
(a) 4g
(b) 2g
(c) \frac{g}{2}

(d) \frac{g}{4}

\frac{g}{4}

51 On mountains our weight will be ………………..as compared to weight on the surface of earth.
(a) Equal
(b) Greater
(c) Less
(d) Zero

Less

52 Weight of the body of mass 10 kg on the surface of moon,
(a) 16 N
(b) 20 N
(c) 26 N
(d) 40 N

16 N

53 What is the mass of an object on the surface of Moon if its mass on Earth’s surface is 10 kg.
(a) 5 kg
(b) 10 kg
(c) 15 kg
(d) 100 kg

10 kg

### Motion of Artificial Satellites

#### Speed in Circular Orbit Calculation

54 The minimum velocity required for an artificial satellite to maintain a stable orbit around Earth?
(a) Escape velocity
(b) Terminal velocity
(c) Orbital velocity
(d) Acceleration velocity

Orbital velocity

55 What are bodies that orbits around larger bodies called
(a) Satellites
(b) Moons
(c) Planets
(d) None of these

Satellites

56 The man-made satellites are called
(a) Natural satellites
(b) Artificial satellites
(d) All of these

Artificial satellites

57 When was the first artificial satellite launched?
(a) 1957
(b) 1967
(c) 1977
(d) 1987

1957

58 Which of the following is NOT a factor affecting the orbital velocity of a satellite?
(a) Mass of the satellite
(b) Mass of the Earth
(c) Altitude of the satellite

Mass of the satellite

59 The motion of an artificial satellite in a circular orbit is an example of:
(a) Translatory motion
(b) Uniform motion
(c) Circular motion
(d) Oscillatory motion

Circular motion

60 What is the shape of the path followed by an artificial satellite around the Earth?
(a) Ellipse
(b) Parabola
(c) Hyperbola
(d) Circle

Ellipse

61 What happens to the orbital velocity of a satellite if its altitude above the Earth’s surface decreases?
(a) Increases
(b) Decreases
(c) Remains the same
(d) None of these

Increases

62 The minimum velocity required for an object to escape the gravitational pull of a celestial body is called:
(a) Orbital velocity
(b) Escape velocity
(c) Terminal velocity
(d) Gravitational velocity

Escape velocity

63 Which of the following quantities is NOT required to calculate the orbital velocity of a satellite?
(a) Mass of the satellite
(c) Mass of the Earth
(d) Altitude of the satellite

Mass of the satellite

64 A satellite in a low Earth orbit will experience more or less gravitational force compared to a satellite in a higher orbit?
(a) Less
(b) More
(c) The same
(d) All of these

More

65 A satellite is revolving around the earth in a circular orbit. If the radius of the orbit is increased from R \ to \ 2R . What will be its velocity?
(a) \sqrt{2v}
(b) 2 \ v
(c) 5 \ v
(d) None of these

\sqrt{2v}

66 An artificial satellite keeps on revolving around the earth in different orbits with uniform speed due to the?
(a) Gravitational force
(b) Frictional force
(c) Electromagnetic force
(d) Normal force

Gravitational force

67 What happens if a satellite’s speed is too low?
(a) It escape earth gravity
(b) It fall back to earth
(c) It becomes a moon
(d) All of these

It fall back to earth

68 What happens if a satellite’s speed is too high?
(a) It escape earth gravity
(b) It fall back to earth
(c) It becomes a moon
(d) All of these

It escape earth gravity

69 What keeps a satellite in orbit?
(a) Its high altitude
(b) Its mass
(c) Its high speed
(d) Its size

Its high speed

70 In a circular orbit, what is the nature of a satellite’s orbital velocity?
(a) It changes constantly
(b) It decreases as it orbits
(c) It increases as it orbits
(d) It remains constant