Newton's Laws

Newton's Laws of Motion
First Law: Objects at rest remain at rest and objects in motion remain in motion in a straight line unless acted upon by an unbalanced force.
Second Law: Force equals mass times acceleration (or f=ma)
Third Law: For every action there is an equal and opposite reaction

Introduction

You step on the gas and your car moves. You kick a soccer ball and it flies through the air. A coconut falls out of a tree and lands on your head. Why did these objects change from sitting still to moving? This module will deal with Dynamics, the study of why things move (actually accelerate). Sir Isaac Newton was the first man to put down rules for force, known as Newton's Laws of Motion. These describe how objects change their motion if a net force is applied to it.

Module Lessons Preview

In this module, we will study the following topics:

What is Newton's First Law and how does it relate to inertia?
How does Newton's Second Law relate to net force, acceleration, and mass?
What is represented in a Free Body Diagram (FBD)?
What is the relationship between forces when we apply Newton's Third Law?

Key Terms

Action/Reaction Pair: Pairs of forces that have the same value but act on different objects.
Force: Any push or pull on an object.
Free Body Diagram (FBD): A diagram that represents an object as a point and then shows all the relative magnitude and direction of all the forces acting on that object as vector arrows.
Inertia: The tendency of an object to resist any change in its motion, measured by the mass of the object.
Mass: A measurement of the amount of matter in an object, measured in kilograms.
Net Force: The vector sum of the forces acting on an object.
Newton's First Law of Motion: An object at rest remains at rest and an object in motion remains in motion unless acted upon by an outside force.
Newton's Second Law of Motion: A net force on an object causes an acceleration that is directly proportional to the net force and inversely proportional to the mass of the object.
Newton's Third Law of Motion: For any force, there is a force equal in magnitude but opposite in direction directed at the object applying the initial force.

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