Physics

Gravitation and Center of Mass

368 Questions

Gravitation and center of mass questions explore gravitational fields, planetary density, and the mechanics of celestial bodies. Test items include calculating gravitational strength on different planets and understanding the Roche Limit. This topic is essential for the physics syllabus of major competitive exams.

Gravitational fieldCenter of massPlanetary densityHill SphereSpace-time curvature

Gravitation and Center of Mass Questions

Multiple choice

As you go to high altitudes, acceleration due to gravity _________.

  1. decreases

  2. increases

  3. remains the same

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Acceleration due to gravity (g) decreases with altitude because g = GM/r², where r is the distance from Earth's center. As altitude increases, r increases, causing g to decrease. This is why objects weigh slightly less at higher altitudes.

Multiple choice

Weight of a man is more ________.

  1. at the equator

  2. at the poles

  3. at the centre

  4. in the space
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Weight (mg) is more at the poles because g is maximum at the poles and minimum at the equator. This happens because: (1) Earth is not a perfect sphere - it's flattened at poles (polar radius < equatorial radius), so you're closer to Earth's center at poles, and (2) centrifugal force at equator slightly reduces effective g.

Multiple choice

If a ball weighs 12 kg on the earth, what will be its weight on the moon?

  1. 2 kg

  2. 6 kg

  3. 12 kg

  4. 24 kg
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Weight on the moon is approximately 1/6th of weight on Earth because moon's gravitational acceleration (g_moon ≈ 1.62 m/s²) is about 1/6th of Earth's (g_earth ≈ 9.81 m/s²). A 12 kg weight on Earth would weigh approximately 12 × (1/6) = 2 kg on the moon. Note: the question uses 'kg' for weight when it should use 'N' for force - mass (12 kg) remains constant.

Multiple choice

The maximum value of g i.e. acceleration due to gravity is _______.

  1. 980 ms-2

  2. 98 ms-2

  3. 9.8 ms-2

  4. 0.98 ms-2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The acceleration due to gravity (g) at Earth's surface is approximately 9.8 m/s². This is the maximum value because g decreases with increasing altitude or depth from the surface. Option A (980) would be in cm/s², not m/s². Option B (98) and D (0.98) are incorrect values.

Multiple choice

The acceleration due to gravity at the centre of the earth is ______.

  1. maximum

  2. the same as that at the surface

  3. zero

  4. minimum
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At Earth's center, a body is equidistant from all surrounding mass. Gravitational forces from all directions cancel out completely, resulting in zero net gravitational force and thus g = 0. Option A is incorrect because g is maximum at the surface, not the center. Option B is wrong since g varies with depth. Option D is misleading - g is zero, not just minimum.

Multiple choice

Gravitational field at a point is ______.

  1. a scalar quantity

  2. a vector quantity

  3. neither scalar nor vector

  4. zero
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A gravitational field has both magnitude and direction - it points toward the mass creating the field. This makes it a vector quantity. Options A and C are incorrect because the field definitely has direction. Option D is wrong because the field strength is non-zero (it's g at that point).

Multiple choice

The weight of an object would be minimum when it is placed ________.

  1. at the north pole

  2. at the south pole

  3. at the equator

  4. at the centre of the earth
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Weight is minimum (zero) at Earth's center because gravitational forces from all surrounding mass cancel completely. At the poles (A and B), weight is maximum due to no centrifugal reduction. At the equator (C), weight is slightly less than at poles due to centrifugal force from Earth's rotation, but still much more than zero at the center.

Multiple choice

Which of the following are significances of Universal Law of Gravitation? (a) It is applicable to every object in the universe. (b) It is the cause of revolution of moon around the earth and revolution of planets around the sun. (c) When an object is immersed fully or partially in a liquid, it experiences an upward force. (d) It explains the cause of neap tide due to moon and sun.

  1. both a and b

  2. both b and c

  3. a, b and c

  4. b, c and d

  5. a, b and d
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Yes, it is the correct answer, as all the three statements mention the importance of the Universal Law of Gravitation.

Multiple choice

Chandrayan was launched from ISRO to explore the moon in 2008. A change in mass (M) and weight (W) of the satellite was observed. Which of the following option shows it correctly?

  1. M decreased and W was constant

  2. M decreased and W increased

  3. M was constant and W increased

  4. M was constant and W decreased

  5. M increased and W was constant
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Yes, it is the correct answer. Mass will remain the same whether that object is on the moon, on the earth or anywhere in the universe. Weight of an object on the earth is the force by which earth attracts that very object towards it, which becomes less on moon.

Multiple choice

Which of the following shows the maximum force of attraction between the two objects A and B? (a) A with mass 30 kg and B with mass 35 kg and distance between them is 10 m. (b) A with mass 50 kg and B with mass 35 kg and distance between them is 8 m. (c) A with mass 20 kg and B with mass 30 kg and distance between them is 20 m. (d) A with mass 10 kg and B with mass 15 kg and distance between them is 5 m. (e) A with mass 30 kg and B with mass 20 kg and distance between them is 10 m.

  1. a

  2. b

  3. c

  4. d

  5. e
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yes, it is correct as this shows the maximum force of attraction between A and B. F = G x M x m / D x DF = G x 27.3 N

Multiple choice

The mass of the earth is approximately

  1. 6 × 1022 kg

  2. 6 × 1023 kg

  3. 6 × 1024 kg

  4. 6 × 1020 kg

  5. 6 × 1021 kg
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As we know that, F = GMm/ R2.
Where G = Gravitational constant, M = mass of the earth, m = mass of the another body at the surface of the earth, R = Radius of the earthor, F= ma ( here a = g) ma = GMm/ R2 Or M = g, R2/ GOr M = 9.8 (6.4×106)2 / 6.67 × 10 – 11 = 6× 1024 kg. It is the correct option

Multiple choice

Choose the correct option:

  1. G is the acceleration due to gravity and g is the Universal Gravitation Constant

  2. G is the Universal Gravitation Constant and g is the acceleration due to gravity

  3. Both G and g are the acceleration due to gravity

  4. Both G and g are the Universal Gravitation Constant

  5. Both 1 and 2 are correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

G is numerically equal to the force of attraction between two unit mass, placed at a unit distance. It is denoted by G, the acceleration produced in the motion of body under the effect of gravity is called acceleration due to gravity. It is denoted by g, so it is the correct option.