http://www.ck12.org Chapter 4. Newton’s Laws
CHAPTER
4 Newton’s Laws
Chapter Outline
4.1 Newton’s First Law
4.2 NEWTON’SSECONDLAW
4.3 NEWTON’STHIRDLAW
4.4 FREEBODYDIAGRAMS
4.5 Friction
4.6 Pressure and Force
4.7 Types of Forces
4.8 PROBLEMSOLVING 1
Introduction
The Big Idea
Applied forces may cause objects to accelerate. All forces come in pairs because they arise in the interaction of two
objects —you can’t push without being pushed back! The more force applied, the greater the acceleration that is
produced. Objects with high masses are difficult to accelerate without a large force. In the absence of applied forces,
objects move in a straight line at a constant speed (or remain at rest). In formal language:
4.2 Newton’s Second Law
Every body continues in its state of rest, or of uniform motion in a right(straight)line, unless it is compelled
to change that state by forces impressed upon it.4.3 Newton’s Third Law
The change of motion is proportional to the motive force impressed; and is made in the direction of the right
(straight)line in which that force is impressed.
Newton’s Third Law
To every action there is always opposed an equal reaction: or, the mutual actions of two bodies upon each
other are always equal, and directed to contrary parts.