# Chapter 4: Newton's Three Laws

Difficulty Level:

**At Grade**Created by: CK-12

Newton's three Laws of Motion are the core of our understanding of *force*, which is how objects affect each others' motion. In this chapter, we will cover the definition of force, an object's innate resistance to being moved by force – called *inertia* – and how forces interact with each other.

Chapter Outline

### Chapter Summary

#### Newton’s Three Laws

- Newton’s First Law of Motion: An object remains at rest or in a state of uniform motion unless acted upon by an unbalanced force.
- Newton’s Second Law of Motion: The acceleration, \begin{align*}a\end{align*}, that an object experiences is directly proportional to the net force acting on the object, \begin{align*}\sum F\end{align*} or \begin{align*}(F_{net})\end{align*}, upon it and inversely proportional to its mass, \begin{align*}m\end{align*}. \begin{align*}\sum F = F_{net} = Ma\end{align*}
- Newton’s Third Law of Motion: Whenever two objects interact they must necessarily place equal and opposite forces upon each other. \begin{align*}F_{ab} = - F_{ba}\end{align*}

#### Solving Problems Using Newton’s Laws

Steps:

- Read the problem carefully and draw a rough sketch of what is happening.
- Draw a careful free-body diagram for each object in the problem.
- Write an equation associated with each free-body diagram using Newton’s Second Law.
- Add other equations if necessary.
- Solve the system of simultaneous equations.
- Check your results to see if they are physically reasonable.

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Description

Covers inertia, force, how force causes acceleration, and how objects cause force against each other.

Difficulty Level:

At Grade
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Date Created:

Jun 10, 2014
Last Modified:

Mar 30, 2016
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