Free Gravitation MCQs with Answers

61. If the value of G is doubled, the value of g:

• A. Is also doubled
• B. Remains the same
• C. Becomes one half
• D. Become a quarter of the original value

Explanation: Correct Answer: A If the value of universal constant G is doubled, the value of g is also doubled. according to the given formula: g=GM/R2 G and g are directy proportional to each other if M and R are kept constant.

62. If the mass of body moves towards the axis of rotation, its moment of inertia:

• A. Increased
• B. Decreased
• C. Remained constant
• D. None of the above

Explanation: If the mass of a body moves toward the axis of rotation, the moment of inertia of the body decreases. The moment of inertia (II is a measure of an object's resistance to changes in its rotation. It depends on both the mass distribution and the axis of rotation. The formula for the moment of inertia of a system of particles is given by: I=∑mi ⋅ri2 If the mass is moved towards the axis of rotation, reducing the value of "r", the moment of inertia will decrease. Conversely, if the mass is moved away, the moment of inertia will increase.

63. _ force is responsible for the motion of the planets around the sun:

• A. Gravitation
• B. Weak
• C. Strong
• D. None of these

Explanation: The gravitational force is responsible for the motion of planets around the Sun. According to Newton's law of universal gravitation, every point mass attracts every other point mass in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. For an object like a planet orbiting a star, gravity is the centripetal force that keeps it in orbit. The gravitational force between the sun (mass M) and the planets (mass m) is given by the formula: F= GMm/r2

64. According to Newton's law of gravitation, force is_ _ proportional to the product of their masses:

• A. Directly
• B. Universal
• C. Inversely
• D. None of these

Explanation: According to Newton's law of gravitation, force is directly proportional to the product of the masses of two objects. The law is expressed mathematically as: F=Gm1m2/r2 where: ( F ) is the gravitational force between the two masses, (G) is the gravitational constant, (m1) and (m2) are the masses of the two objects, and (r) is the separation between the centers of the masses.

65. Force is _ proportional to the square of the distance between the centers of the masses of two objects:

• A. Directly
• B. Inversely
• C. Gravitation
• D. None of these

Explanation: The force between two objects is inversely proportional to the square of the distance between their centers of mass. This statement is known as Newton's law of universal gravitation. Mathematically, the law is expressed as: F= Gm1m2/r2 where: ( F ) is the gravitational force between the two objects, ( G ) is the gravitational constant, ( m1 ) and ( m2 ) are the masses of the two objects, and ( r ) is the distance between the centers of mass of the two objects.

66. "G" is known as _:

• A. Gravitation of the earth
• B. Universal gravitational constant
• C. Gravitational distance
• D. None of these

Explanation: "G" in the equation for the gravitational force is known as the gravitational constant. The gravitational constant is denoted by the symbol \( G \) and is a fundamental constant of nature. Its approximate value is \( 6.67430 \times 10^{-11} \ \text{N} \cdot \text{m}^2/\text{kg}^2 \). It plays a crucial role in describing the strength of the gravitational interaction between two masses in Newton's law of universal gravitation.

67. The value of universal constant "G" is_.

• A. 4.49 x 10^12 Nm
• B. 6.67 x 10^-9 Nm
• C. 6.67 x 10^-11 Nm2/kg2
• D. 6.67 x 10^-6 Nm2/kg2

Explanation: "G" in the equation for the gravitational force is known as the gravitational constant. The gravitational constant is denoted by the symbol \( G \) and is a fundamental constant of nature. Its approximate value is \( 6.67430 \times 10^{-11} \ \text{N} \cdot \text{m}^2/\text{kg}^2 \). It plays a crucial role in describing the strength of the gravitational interaction between two masses in Newton's law of universal gravitation.

68. The gravitational force between two bodies is _, _ pair:

• A. Normal and general
• B. Positive and negative
• C. Negative and positive
• D. Action and reaction

Explanation: Newton's third law of motion states that for every action, there is an equal and opposite reaction. When it comes to gravitational forces, this law applies as well. Consider two objects with masses ( m1 ) and ( m2 ), and let ( F12) be the gravitational force exerted by ( m1 ) on ( m2 ). According to Newton's third law: 1. Action: ( m1 ) exerts a gravitational force ( F2) on ( m2 ). 2. Reaction: ( m2 ) simultaneously exerts an equal and opposite gravitational force ( F21) on ( m1 ). Mathematically, this can be expressed as: F(12} = -F{21) Here, the minus sign indicates that the forces are in opposite directions, as dictated by Newton's third law. The magnitudes of the forces are equal, but their directions are opposite. This is true for any two masses in the universe; the gravitational force between them forms an action-reaction pair according to Newton's third law.

69. Two bodies "A" and "B" exert gravitational forces of "F1" and "F2" on one another, then we can say that both forces are equal in magnitude but _ in direction:

• A. Action
• B. Reaction
• C. Opposite
• D. None of these

Explanation: Newton's third law of motion states that for every action, there is an equal and opposite reaction. When it comes to gravitational forces, this law applies as well. Consider two objects with masses ( m1 ) and ( m2 ), and let ( F12) be the gravitational force exerted by ( m1 ) on ( m2 ). According to Newton's third law: 1. Action: ( m1 ) exerts a gravitational force ( F2) on ( m2 ). 2. Reaction: ( m2 ) simultaneously exerts an equal and opposite gravitational force ( F21) on ( m1 ). Mathematically, this can be expressed as: F(12} = -F{21) Here, the minus sign indicates that the forces are in opposite directions, as dictated by Newton's third law. The magnitudes of the forces are equal, but their directions are opposite. This is true for any two masses in the universe; the gravitational force between them forms an action-reaction pair according to Newton's third law.

70. Cavendish used his method to find the value of _:

• A. R
• B. G
• C. -R
• D. R2

Explanation: Henry Cavendish used his method to determine the density of the Earth and, from there, to calculate the gravitational constant ( G ). He conducted the Cavendish experiment, also known as the Cavendish torsion balance experiment, in 1797-1798. The experiment involved a torsion balance, a horizontal bar suspended from a thin wire. Two small lead spheres were attached to each end of the bar, and two larger lead spheres were positioned nearby. The gravitational attraction between the small and large spheres caused the bar to twist, and by measuring this twist, Cavendish could determine the gravitational force and, subsequently, the density of the Earth. Cavendish did not directly calculate the value of ( G ), but his measurements provided the necessary data for later scientists, like C.F. Gauss, to determine the value of the gravitational constant. The modern accepted value for ( G ) is approximately 6.67430 x 10^{-11} Nm2/Kg2