Inertia MCQs Quiz | Class 9

Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the Definition of Inertia and its types (Inertia of Rest, Inertia of Motion, and Inertia of Direction). Attempt these 10 MCQs to test your conceptual understanding, check your score, and download the solution PDF for revision.

Inertia: Definition and Concept

Inertia is the inherent property of an object to resist any change in its state of rest or of uniform motion in a straight line. The term was introduced by Galileo Galilei, and it forms the basis of Newton’s First Law of Motion, often called the Law of Inertia.

The measure of inertia is Mass. An object with greater mass has greater inertia. For example, it is harder to push a loaded truck than an empty car because the truck has more mass and thus more inertia.

Types of Inertia

Inertia is classified into three main types based on the state the object resists changing:

  • Inertia of Rest: The tendency of a body at rest to remain at rest unless acted upon by an external force. Example: When a bus starts suddenly, passengers fall backward.
  • Inertia of Motion: The tendency of a body in uniform motion to remain in motion unless acted upon by an external force. Example: When a moving bus brakes suddenly, passengers fall forward.
  • Inertia of Direction: The inability of a body to change its direction of motion by itself. Example: When a car takes a sharp turn, passengers are thrown outwards.

Comparison Table

Type Key Characteristic Common Example
Inertia of Rest Resists starting motion Dust falls when beating a carpet
Inertia of Motion Resists stopping Athlete runs before jumping
Inertia of Direction Resists turning Mud flying off a rotating wheel

Quick Revision Points

  • Inertia depends only on mass, not on velocity or shape.
  • A heavier object has more inertia than a lighter object.
  • Newton’s First Law defines inertia qualitatively.
  • Seatbelts in cars work against inertia of motion to prevent injury.