Gravitation (Concept) MCQs Quiz | Class 9

Class: IX | Subject: Science (Code 086) | Unit: Unit III: Motion, Force and Work | Topic: Gravitation | Coverage: Meaning of gravitation; attraction between masses. Click ‘Submit Quiz’ to check your score and download the answer key PDF.

Understanding Gravitation

Gravitation is a fundamental force of nature that causes a mutual attraction between all objects with mass. In Class IX Science (Unit III), we explore how this force governs the motion of celestial bodies and objects on Earth.

1. The Universal Law of Gravitation

Formulated by Sir Isaac Newton, the Universal Law of Gravitation states that every object in the universe attracts every other object with a force that is:

  • Directly proportional to the product of their masses (M and m).
  • Inversely proportional to the square of the distance (d) between their centers.

Mathematically, it is expressed as: F = G (Mm / d^2), where G is the Universal Gravitational Constant.

2. Importance of the Universal Law

The gravitational force is responsible for several critical phenomena:

  • The force that binds us to the Earth.
  • The motion of the Moon around the Earth.
  • The motion of planets around the Sun.
  • The tides due to the Moon and the Sun.

3. Quick Facts

Parameter Details
Symbol for Force F (Newton, N)
Constant (G) 6.673 x 10^-11 Nm^2/kg^2
Nature Always attractive, never repulsive
Range Long-range force (infinite range)

Extra Practice Questions

  1. What happens to the force if the mass of one object is doubled? (Ans: Force doubles)
  2. What is the unit of G? (Ans: Nm^2/kg^2)
  3. Does gravitation act in a vacuum? (Ans: Yes)
  4. Who determined the value of G? (Ans: Henry Cavendish)
  5. Is gravitational force a contact force? (Ans: No, it is a non-contact force)