Universal Law of Gravitation MCQs Quiz | Class 9

Test your understanding of Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the Universal Law of Gravitation, including its statement, formula, and the dependence of force on masses and distance. Solve these 10 MCQs to check your grasp of the concepts, then submit to view your score and download the answer key PDF.

Universal Law of Gravitation: Overview

The Universal Law of Gravitation was proposed by Sir Isaac Newton. It states that every object in the universe attracts every other object with a force that is directed along the line joining the centers of the two objects.

The Mathematical Formula:

The magnitude of the gravitational force (F) between two objects of masses M and m separated by a distance d is given by:

F = G (M x m) / d2

Where G is the Universal Gravitational Constant.

Key Factors Affecting Gravitational Force

  • Product of Masses: The force is directly proportional to the product of the masses (M x m). If the mass of one object doubles, the force doubles. If both masses double, the force becomes four times stronger.
  • Square of Distance: The force is inversely proportional to the square of the distance (1/d2). This is known as the Inverse Square Law. If the distance between objects is doubled, the force decreases to one-fourth. If distance is halved, force becomes four times stronger.

Universal Gravitational Constant (G)

The value of G is constant everywhere in the universe. Its accepted value is approximately 6.673 x 10-11 N m2 kg-2. It was determined experimentally by Henry Cavendish.

Importance of the Law

This law explains several phenomena, including:

  • 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 caused by the Moon and the Sun.

Quick Revision List

  • Force is always attractive in nature.
  • Gravitational force is a central force (acts along the line joining centers).
  • It is independent of the medium between the objects.
  • G is a scalar quantity.

Extra Practice Questions

  1. What is the unit of G in SI system? (Answer: N m2 kg-2)
  2. Who determined the value of G? (Answer: Henry Cavendish)
  3. If distance is tripled, how does force change? (Answer: It becomes 1/9th)
  4. Is gravitational force repulsive? (Answer: No, always attractive)
  5. Does G change on the Moon? (Answer: No, G is constant everywhere)