Newton's Laws of Motion: Third Law
John Smith
9 min read
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Study Guide Overview
This study guide covers Newton's Third Law, focusing on action-reaction pairs, their characteristics, and identification. It explores common force pair examples like friction and tension, and uses Atwood machines as a practical application of the law. The guide also provides a derivation of the acceleration formula for Atwood machines, common mistakes, and exam tips including free-body diagrams. Finally, it includes practice multiple-choice and free-response questions for exam preparation.
#AP Physics C: Mechanics - Newton's Third Law Study Guide š
Hey there, future physics champ! Let's break down Newton's Third Law and make sure you're totally ready to ace that exam. This guide is designed to be your go-to resource, especially the night before the test. Let's get started!
#Newton's Third Law of Motion: Action-Reaction Pairs
For every action, there is an equal and opposite reaction.
It's more than just a catchy phrase; it's a fundamental principle! Let's make sure you understand it inside and out.
Newton's Third Law is all about force pairs. These forces are:
- Always between two interacting objects.
- Always the same type of force (e.g., both are tension, both are gravitational).
- Always equal in magnitude but opposite in direction.
#Key Concepts:
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Action-Reaction: If object A exerts a force on object B, then object B exerts an equal and opposite force on object A.
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Simultaneous Forces: These forces occur at the same time; one doesn't cause the other.
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Universal Application: This law applies to all forces: gravity, electromagnetism, etc.
Think of it like a handshake: When you push on someone's hand, they push back on yours with the same force, but in the opposite direction.
#Visualizing Force Pairs
A visual representation of Newton's Third Law. The force exerted by the hand on the wall is equal and opposite to the force exerted by the wall on the hand.
Another example of action-reaction pairs. The force of the foot on the ball is paired with the force of the ball on the foot.
#Identifying Force Pairs
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Identify the interacting objects: Who is pushing on whom?
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Determine the force type: Is it tension, friction, gravity, etc.?
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Visualize the direction: Are the forces acting in opposite directions?
When drawing free-body diagrams, use the same color or circle force pairs to help visualize them. This can prevent errors when setting up equations!
#Common Force Pairs:
- Friction between two surfaces
- Tension in a rope or cable
- Air resistance on a moving object
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