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

If the distance between two planets is increased by a factor of 3, the gravitational force of attraction between them will be _________.

  1. increased by a factor of 3

  2. reduced by a factor of 3

  3. increased by a factor of 9

  4. reduced by a factor of 9

  5. independent of radius
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The gravitational force between two bodies is given by F = GMm/R2 If the distance between the two bodies R is increased by a factor of 3, the gravitational force F will reduce by a factor of 9.

Multiple choice

The acceleration due to gravity is zero at __________.

  1. the equator

  2. poles

  3. sea levels

  4. the centre of the earth

  5. same at all places
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The value of g does vary with altitude or height from the ground. The variation with height from the equation: g = GM/(RE + h)2

Multiple choice

At the centre of the earth

  1. mass of a body is zero, but weight is not zero.

  2. mass of a body is not zero, but weight is zero.

  3. both mass and weight of a body is zero.

  4. both mass and weight of a body is not zero.

  5. the value of g is 9.8.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Weight depends on acceleration due to gravity and its value varies from place to place . So, it may be zero.

Multiple choice

Consider the following statements:

  1. When a person is standing on a weighing scale in a lift, which is moving upwards, the weighing scale shows lesser weight.2. The weight of an object would be minimum, when it is placed at the north pole of earth.
  2. The weight is a measure of the quantity of matter.

Which of the given statements is/are incorrect?

  1. Only (1)

  2. Only (1) and (2)

  3. Only (2) and (3)

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

(1) Statement (1) is wrong. When a person is standing on a weighing scale in a lift, which is moving upwards, the weighing scale shows more weight. (2) Statement (2) is wrong. The weight of an object would be minimum, when it is placed at the centre of earth because it experiences gravitational pull from all the sides. Thus, the net weight of an object remains to be zero. (3) Statement (3) is wrong. Mass is a measure of the quantity of matter, whereas weight is a measure of force.

Multiple choice

Consider the following statements:

  1. The gravitational force with which the earth attracts the moon is equal to the force with which the moon attracts the earth.
  2. The weight of a body at the centre of earth is slightly less than that at the surface.

Which of the given statements is/are correct?

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement (1) is correct. The gravitational force with which the earth attracts the moon is equal to the force with which the moon attracts the earth. If it is decreased, the earth attracts the moon. Statement (2) is wrong. The weight of a body at the centre of Earth is zero, due to lack of gravitational force.

Multiple choice

Consider the following statements:

  1. The weight of a body on moon would increase compared to the weight on the Earth.
  2. It is advantageous to run before taking long jump.

Which of the given statements is/are correct?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement 1 is incorrect. The weight of the body would decrease. Weight is the function of gravity. As moon's gravity is much lesser than Earth. So, the weight of the body on the moon would decrease. Statement 2 is correct. An athlete often runs before taking a long jump because by running first he brings himself in the state of motion and then it becomes easier for him to take a long jump.

Multiple choice

Consider the following statements:

  1. The weight of an object would be minimum, when it is placed at the centre of earth.
  2. A stone is dropped from a cliff against a strong breeze. The breeze exerts a steady horizontal force on the stone as it falls. The path of the stone is in straight line.

Which of the given statements is/are correct?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement 1 is correct. The weight of an object would be minimum, when it is placed at the centre of earth because it experiences gravitational pull from all the sides. Thus, the net weight of an object remains to be zero. Statement 2 is also correct. The horizontal force will drive away the stone and the gravitational pull will bring it down. Due to strong breeze, it drags in straight path.

Multiple choice

Which of the following statements is/are correct?

  1. Average density of the earth is 5.5 g/cm3.
  2. Average density of the core of the earth is 11.0 g/cm3.
  3. Average density of the earth's crust is 2.7 to 3.3 g/cm3.

  1. All 1, 2 and 3

  2. Only 1 and 2

  3. Only 2 and 3

  4. Only 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Density of the layers of the earth: Continental crust: 2.7 to 3.0 g/cm3 Oceanic crust: 3.0 to 3.3 g/cm3 Mantle (silicates): 3.3 to 5.7 g/cm3 Outer core (liquid): 9.9 to 12.2 g/cm3 Inner core (solid): 12.6 to 13.0 g/cm3 Average density of the earth: 5.5 g/cm3

Multiple choice

Which of the following is/are correct?

  1. The average specific gravity of the earth is more than the average specific gravity of the crust.
  2. On the basis of mechanical properties, the earth can be divided into crust, mantle and core.

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Density of the layers of the earth: Continental Crust: 2.7 to 3.0 gm/ cm3 Oceanic Crust: 3.0 to 3.3 gm/ cm3 Average density of the earth: 5.5 gm/ cm3 The earth can be divided into crust, mantle and core on the basis of its chemical composition.

Multiple choice

A person weighs 75 N on earth. What does it mean?

  1. The person is attracted by the earth with a force of 75 N.

  2. The person attracts the earth with a force of 75 N.

  3. Both (1) and (2)

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since both reasons are included in option 3, so option (3) is correct.