Gravity MCQ Quiz - Objective Question with Answer for Gravity - Download Free PDF

The Correct answer is 730 N.

Key Points

• The weight of an object is the force it experiences due to gravity, calculated using the formula: Weight = Mass × Acceleration due to gravity (g).
• Here, the given mass of the object is 74.5 kg, and the value of g (acceleration due to gravity) is 9.8 m/s².
• Using the formula: Weight = 74.5 × 9.8 = 730.1 N.
• The result is approximately 730 N, which matches the correct option.
• Weight is a vector quantity, meaning it has both magnitude and direction. On Earth, the direction is toward the center of the planet.
• Weight varies depending on the gravitational pull, so it would be different on other celestial bodies with different gravitational values.
• The use of 9.8 m/s² as the gravitational constant is standard for calculations on Earth's surface.

 Additional Information

• Key Concept: Weight vs Mass
  • Mass is a measure of the amount of matter in an object, and it is constant regardless of location. It is measured in kilograms (kg).
  • Weight, on the other hand, is the force exerted by gravity on an object’s mass. It depends on the gravitational acceleration at a specific location and is measured in newtons (N).
• Scientific Context
  • The formula Weight = Mass × g is derived from Newton's Second Law of Motion, which states that Force = Mass × Acceleration.
  • In the context of weight, the acceleration due to gravity (g) acts as the acceleration component.
• Importance of Accurate Calculations
  • Understanding weight is crucial in fields like engineering, space exploration, and physics, where precise force measurements are required.
  • In everyday life, weight is used in designing structures, manufacturing, and medical applications like determining body weight.

The Correct answer is 3.35 × 10^-11 N.

Key Points

• The given problem is about calculating the gravitational force between two objects using Newton's Law of Universal Gravitation.
• The formula for gravitational force is F = G × (m₁ × m₂) / r², where:
  • F is the gravitational force.
  • G is the gravitational constant = 6.7 × 10^-11 N·m²/kg².
  • m₁ and m₂ are the masses of the two objects = 80 kg and 250 kg respectively.
  • r is the distance between the centers of the two objects = 200 m.
• Substituting the values into the formula:
  • F = (6.7 × 10^-11) × (80 × 250) / (200)²
  • First, calculate the numerator: 80 × 250 = 20000.
  • Next, calculate the denominator: (200)² = 40000.
  • Now, compute the force: F = (6.7 × 10^-11) × (20000 / 40000).
  • F = (6.7 × 10^-11) × 0.5.
  • F = 3.35 × 10^-11 N.
• Hence, the gravitational force between the two objects is 3.35 × 10^-11 N.

 Additional Information

• Key Concepts:
  • Gravitational Force: It is a universal force of attraction that acts between all objects with mass.
  • Gravitational Constant (G): The value of G is constant in nature and is equal to 6.7 × 10^-11 N·m²/kg².
  • This force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between them.
  • The gravitational force is extremely weak for small masses but becomes significant for massive objects like planets, stars, and moons.

The correct answer is Option 3

Explanation:

• Mass is an intrinsic property — it does not change with location (Earth or Moon).
• A two-pan balance compares the mass of an object to known masses by balancing them. Since gravitational pull affects both pans equally, it measures mass, not weight.
• Therefore, the measured mass of an object on Earth and on the Moon using a two-pan balance will be the same.
• If mass remains constant, then plotting "Measurements on Moon" vs. "Measurements on Earth" should yield a straight line passing through the origin with slope = 1 (i.e., y = x).

The correct answer is At the centre of the Earth.

• The centre of the Earth is such that if we are at that place, the mass around us can be considered to be condensed at the surface of the Earth itself, i.e considering the Earth as a spherical shell.
• Inside a spherical shell, there is no change in potential as one moves inside, and since only a change in potential implies a force there is no force.
• Hence the acceleration due to gravity is zero at the centre of the Earth.

CONCEPT:

Mass and Weight on Earth vs Moon

• Mass is a constant property of an object and does not change with location. Therefore, the mass of an object on Earth is the same as its mass on the Moon.
• Weight depends on the gravitational force acting on an object. The gravitational force on the Moon is approximately 1/6th of that on Earth, which means the weight on the Moon is 1/6th of the weight on Earth.
• The relationship between mass on Earth and mass on the Moon is a straight line with a slope of 1, as mass is constant.
• The relationship between weight on Earth and weight on the Moon is also linear but with a slope of 1/6, indicating that the weight on the Moon is much smaller than on Earth.

EXPLANATION:

• The graph of Mass on Earth vs Mass on Moon will be a straight line with a slope of 1, showing a one-to-one relationship.
• The graph of Weight on Earth vs Weight on Moon will also be linear but with a slope of 1/6, since the weight on the Moon is 1/6th of the weight on Earth.
• Therefore, the correct pair of graphs would be:
  • The graph for Mass shows a slope of 1.
  • The graph for Weight shows a slope of 1/6.

Therefore, the correct answer is Option 2.

The correct answer is At the centre of the Earth.

• The centre of the Earth is such that if we are at that place, the mass around us can be considered to be condensed at the surface of the Earth itself, i.e considering the Earth as a spherical shell.
• Inside a spherical shell, there is no change in potential as one moves inside, and since only a change in potential implies a force there is no force.
• Hence the acceleration due to gravity is zero at the centre of the Earth.

• Let the mass of the earth be M.
• Mass of the other object on earth is m.
• We know the value of Gravitational Constant (G) = 6.67259 × 10^-11 Nm²/kg².
• We know the formula for the force between two objects (F) = G m¹ m²/r².
• Now the radius of the earth (r) = 6.3781 × 10⁶ m.
• We know that F = mg
• Now by substituting the values, we get mg = G M m/r².

M = g r²/G

M = (9.81) (6.3781 × 10⁶)²/6.67259 × 10^-11

M = 6 × 10²⁴ kg.

The mass of the earth (M) is 6 × 10²⁴ kg.

The correct answer is 127.14 N.

Concept:

• Mass: It is defined as the amount of matter it contains.
  • It is measured in kg /g /milligram etc.
  • It is a scalar quantity and has only magnitude.
  • It is not changing due to the position.
  • It is measured with Physical balance, beam balance, etc.

• Weight: It is defined as a measure of the pull of gravity on an object.
  • It is a kind of force and measured in Newton.
  • It is measured as weight (W) = mass (M) × gravity (acceleration due to gravity).
  • It is a vector quantity as it has magnitude as well as direction.
  • It could change according to position, like on the moon or any other planet.
  • It is measured with a spring balance.

Calculation:

Given, M = 78 Kg and g = 1.63 m/s²

W = M × g ⇒ 78 × 1.63 = 127.14 Newton

Hence the weight on the moon of the man is 127.14 N

Mistake Points

Do not go blindly with 1/6 of weight terms on the moon.

Here already given the acceleration on moon 1.63 m/s² 

• Weight is a measure of the force of gravity acting on an object.

Concept:

Unit	Definition
Weight	It is a product of mass and acceleration due to gravity
Acceleration	Acceleration is defined as the rate of change of velocity
Momentum	Momentum is defined as the product of mass and velocity
Impulse	The product of force and time is defined as the impulse.

Explanation:

From the above explanation, we can see that

The gravitational pull by the earth is equal to the weight of the object.
The weight of any object on the planet is given by:

Weight (W) = m g = Force due to gravity

Where

m is mass

g is acceleration due acceleration of the planet.

The correct answer is 40m.

Key PointsInitial velocity(u) = 30m/s

Acceleration due to gravity(g)= 10 m/s2

Time (t) = 4 s

Using the equation,

S = Ut + 1/2 × a× t²

S = 30 × 4 + 1/2 ×  (-10) × 4× 4 

= 120 - 80

= 40 m

The correct answer is 60 kg.

Key Points

• The mass of man on the surface of the moon will remain the same as on earth.
• Mass doesn’t change according to location.
• The mass of a body is the same on Earth and Moon and is equal to 60kg.
• Mass is the measure of the amount of matter in a body.
• The SI unit of mass is kilogram (kg).
• Mass is a scalar quantity and It has magnitude.
• The mass of a body is not dependent on time.
• Mass is not dependent on gravity.
• Mass can never be zero.

Mistake Points

• Weight is defined as a measure of the gravitational force on that body at that place.
• Weight = Mass x Surface Gravity.
  • Surface Gravity on Moon = 
  • Surface Gravity on Earth= 9.8 m/s².
• Weight on moon= 98 N.

The correct answer is Galileo Galilei.

Key Points

• Galileo Galilei was the first to conclude that in vacuum all objects fall with the same acceleration g and reach the ground at the same time.
• The acceleration of the object equals the gravitational acceleration.
  • The mass, size, and shape of the object are not a factor in describing the motion of the object.
  • So all objects, regardless of size or shape, or weight, free fall with the same acceleration.
  • In a vacuum, a feather falls at the same rate as a ball.
  • The remarkable observation that all free-falling objects fall with the same acceleration was first proposed by Galileo Galilei.

Important Points

• Galileo conducted experiments using a ball on an inclined plane to determine the relationship between the time and distance traveled.
  • He found that the distance depended on the square of the time and that the velocity increased as the ball moved down the incline.
  • The relationship was the same regardless of the mass of the ball used in the experiment.
  • The experiment was successful because he was using a ball for the falling object and the friction between the ball and the plane was much smaller than the gravitational force.

• The force of gravitation between two bodies in the universe does not depend on the sum of their masses.
• It depends on distance, gravitational constant, and the product of their masses.
• The strength of the gravitational force depends on distance and mass.
• Gravitational force is that which attracts any 2 objects with mass.

The correct answer is Option (4) i.e.​ (6.67 × 10-8) c.g.s unit.

Mistake Points

•  The value of universal gravitational constant G in CGS system (Centimeter, Gram, Second) is 6.67 × 10-8 dyne cm2gm-2.
• The value of the gravitational constant in MKS system (Meter, Kg, Second) is G = 6.67×10−11 m³kg−1s−2.

Explanation:

• Universal Gravitational Constant (G): The universal constant relating force to mass and distance in Newton's law of gravitation (G), constant of gravitation, gravitational constant type of constant, a number representing a quantity assumed to have a fixed value in a specified mathematical context.
• Value of G = 6.67 × 10-8  c.g.s. Unit.
• Mathematical form: 
  • F = Gravitational Force.
  • M1 & M2 = Mass of 2 different objects which attract each other.
  • G = Universal gravitational constant.

• From this above equation, we can say that the gravitational force is the direct proportionate with the mass of two significant objects but the inverse proportional with the square of the distance(R) between those two objects.

Gravitational force: 

• The gravitational force (F) is a force that attracts any two objects with a mass within a universe.

• Every object, including you, is pulling on every other object in the entire universe. This is called Newton's Universal Law of Gravitation.

• Example of Gravitational force (F):
  1) The force that holds the gases in the sun.
  2) The force that causes a ball you throw in the air to come down again.

The correct answer is Mass.

• The acceleration (Acceleration due to gravity) experienced by an object during a free fall is independent of its mass.
• This acceleration is called acceleration due to the earth’s gravitational force. It is denoted by g.
• The unit of g is ms^-2.

As we know that

F = G.M.m/r² = mg       (F= ma , Second law of Newton)

Where F is the gravitational force, G is universal gravitation, M mass of earth, and m is the mass of the object(body). 
canceling out the Mass of the object (m)
we get;

g = G.M/r² 

So we can see that acceleration due to gravity(g) is independent of the mass of the object(body).