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  1. AP Physics 1 Revised
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Newton's First Law

Noah Martinez

Noah Martinez

7 min read

Next Topic - Newton's Second Law

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Study Guide Overview

This study guide covers Newton's First Law of Motion, focusing on inertia, translational equilibrium, and inertial reference frames. It explains balanced vs. unbalanced forces, calculating net force using vector components, and the conditions for constant velocity. It also includes practice questions and exam tips covering static and dynamic equilibrium.

#Newton's First Law: Inertia and Equilibrium

#Introduction

Newton's First Law, also known as the law of inertia, is a cornerstone of physics. It essentially says that objects like to keep doing what they're already doing. 💡 This means an object at rest stays at rest, and an object in motion stays in motion with the same velocity, unless a net force acts on it. This concept is crucial for understanding translational equilibrium and how forces affect motion.

Key Concept

Newton's First Law is all about understanding that objects resist changes in their state of motion. A net force is required to cause acceleration.

#Conditions for Constant Velocity

#Vector Sum of Forces

  • Calculating the net force 🎯 is key: you need to add all forces acting on an object as vectors. This means considering both their magnitude and direction.
  • Forces in the same direction are added, while forces in opposite directions are subtracted.
  • If forces act at angles, you'll need to break them into components (x and y) before adding them up.

#Translational Equilibrium

  • Translational equilibrium occurs when the vector sum of all forces acting on an object equals zero. This means there's no net force, and thus no acceleration.

  • Mathematically, it's represented as: SigmaFi=0Sigma F_{i} = 0SigmaFi​=0

  • Where Σ\SigmaΣ represents the sum of all forces (FiF_{i}Fi​) acting on the system, and iii denotes each individual force.

  • An object in translational equilibrium can be either at rest (static equilibrium) or moving at a constant velocity (dynamic equilibrium).

  • Example: A book on a table is in static equilibrium; gravity pulls down, and the table pushes up with an equal force.

Common Mistake

Students often forget that forces are vectors. Make sure to consider both magnitude and direction when calculating net force. Always use vector components if forces are at an angle.

#Newton's First Law (Law of Inertia)

  • Also known as the law of inertia ⚖️, it states that an object will maintain its state of m...
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Question 1 of 11

What does inertia describe about an object? 🚀

Its tendency to accelerate

Its resistance to changes in motion

Its ability to exert force

Its mass when at rest