Difficulty: Easy
Correct Answer: Third law of motion
Explanation:
Introduction / Context:
Newton third law of motion is one of the most quoted statements in physics because it explains how forces always come in pairs. When two bodies interact, each one exerts a force on the other, and these forces are equal in magnitude and opposite in direction. The question checks whether you can correctly associate the well known slogan for every action there is an equal and opposite reaction with the correct numbered law in Newton set of three laws of motion.
Given Data / Assumptions:
- The statement describes a pair of forces that are equal and opposite.- The forces act on different bodies that are interacting.- We assume the standard form of Newton laws as taught in basic mechanics.
Concept / Approach:
Newton third law of motion states that whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body. These forces are called action and reaction forces. They always act on different bodies but occur simultaneously. The first law deals with inertia and uniform motion, and the second law relates net force to acceleration. There is no officially recognised fourth law of motion in Newton formulation.
Step-by-Step Solution:
1. Recognise the phrase for every action there is an equal and opposite reaction as the classic wording of Newton third law.2. Remember that this law concerns pairs of forces during interactions, such as a rocket pushing exhaust gases and the gases pushing back on the rocket.3. Recall that Newton first law is about inertia and net zero force, not about paired forces.4. Recall that Newton second law relates net force to acceleration and rate of change of momentum.5. Note again that there is no Newton fourth law in the standard physics curriculum.6. Conclude that the statement must correspond to Newton third law of motion.
Verification / Alternative check:
Examples in textbooks, such as a person walking (foot pushes ground, ground pushes foot), swimming (hand pushes water, water pushes hand), or recoil of a gun (bullet moves forward, gun moves backward), are always described as illustrations of Newton third law. The repeated use of the action reaction phrase in that context confirms that the statement in the question is exactly the verbal expression of the third law.
Why Other Options Are Wrong:
- First law of motion: Addresses what happens when net external force is zero and does not discuss equal and opposite force pairs explicitly.- Second law of motion: Defines the relationship between net force, mass, and acceleration and does not contain the action reaction concept.- Fourth law of motion: No such law exists in Newton classical formulation.
Common Pitfalls:
Students sometimes misremember which numbered law is which, especially under exam pressure. A useful memory key is to associate the phrase action and reaction with the number three, since both words have seven letters but the law is the third. Alternatively, remember the sequence: first law inertia, second law acceleration, third law interaction forces. This ordering will help you avoid mixing up the law numbers in similar questions.
Final Answer:
The statement corresponds to Newton third law of motion.
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