Action and Reaction Forces MCQs Quiz | Class 9

Test your understanding of Newton’s Third Law of Motion for Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz focuses on identifying action-reaction pairs, understanding force magnitudes, and clearing common misconceptions. Submit your answers to view your score and download the PDF result sheet.

Understanding Action and Reaction Forces

Newton’s Third Law of Motion states that “To every action, there is always an equal and opposite reaction.” This fundamental principle helps us understand how forces interact in pairs. In the context of Class IX Science, Unit III, it is crucial to recognize that forces never exist in isolation.

Key Concepts

  • Equal Magnitude: The action force and the reaction force are always equal in strength.
  • Opposite Direction: They always act in opposite directions (180 degrees apart).
  • Different Bodies: Action and reaction forces act on two different objects. This is why they do not cancel each other out to produce zero net force on a single object.
  • Simultaneous Nature: Both forces occur at the exact same instant. One does not cause the other with a time delay.

Common Examples

Scenario Action Force Reaction Force
Walking Foot pushes ground backward Ground pushes foot forward
Swimming Hands push water backward Water pushes swimmer forward
Firing a Gun Gun forces bullet forward Bullet forces gun backward (Recoil)

Addressing Misconceptions

Misconception: Since action and reaction are equal and opposite, they cancel out.

Fact: They do not cancel out because they act on different bodies. Cancellation (equilibrium) only occurs when equal and opposite forces act on the same body.

Practice Questions

  1. Identify the reaction force when a book rests on a table.
  2. Explain why a fireman struggles to hold a hose ejecting water at high speed.
  3. If a mosquito hits a car windshield, which object experiences a greater force? (Answer: Both experience the same force).
  4. Describe the action-reaction pair in a rocket launch.
  5. Why does a rowboat move backward when you push the water forward? (Correction: You push water backward to move forward).