Newton's First Law

Chloe Davis

9 min read

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Study Guide Overview

This study guide covers Newton's First Law of Motion (Inertia). It explains inertia, frames of reference, equilibrium, inertial and gravitational mass, and their relationship. It provides example problems involving these concepts and practice questions for the AP Physics 1 exam. Key equations like F=mg and F=ma are also included.

#AP Physics 1: Newton's First Law - Inertia 🚀

Hey there, future physics ace! Let's break down Newton's First Law, also known as the Law of Inertia, in a way that's super clear and easy to remember. This is a foundational concept, so nailing it down is crucial for the exam. Let's get started!

#1. Newton's First Law: The Law of Inertia

Key Concept

Newton's First Law: An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Basically, things like to keep doing what they're already doing! 💡

Inertia: This is the tendency of an object to resist changes in its state of motion. Think of it as an object's 'laziness' – it doesn't want to speed up, slow down, or change direction unless it absolutely has to.
Frame of Reference: A coordinate system from which motion is observed. An inertial frame of reference is one that is not accelerating (moving at a constant velocity).
Equilibrium: When all forces acting on an object are balanced (net force = 0), the object is in equilibrium. It will either remain at rest or continue moving at a constant velocity.

Memory Aid

Think of a hockey puck: If you slide a hockey puck on perfectly smooth ice (no friction), it would keep going in a straight line at the same speed forever... unless something stops it!

#Inertial Mass

Inertial Mass: A measure of an object's resistance to changes in its motion. The more massive an object is, the harder it is to accelerate.
A small mass (like an ant 🐜) has less inertia and is easily affected by forces.
A large mass (like an elephant 🐘) has more inertia and is harder to move or stop.
Key takeaway: Inertial mass is all about how difficult it is to change an object's velocity.

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Caption: The force applied by the person is the unbalanced force causing the acceleration.

#2. Gravitational vs. Inertial Mass

Gravitational Mass: This is determined by how strongly an object is attracted to other objects due to gravity. It's what we usually think of as 'mass'.
Inertial Mass: This is determined by how much an object resists changes in motion. It's all about how much force it takes to accelerate the object.
The Big Idea: Experimentally, these two types of mass are the same! This is a ...

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