Forces always come in pairs: each force is equal in magnitude, but opposite in direction. Taken together, they would cancel each other out.
This is true of all forces.
If forces always come in pairs that can cancel each other out, why don't we normally see it come into play when we're working on problems? Two main reasons:
The force in the problem is external to the system. The force is guaranteed, and we don't care what happens to the thing causing the force.
The "equal and opposite" force is somehow translated into the Earth, where the planet's large mass makes it negligible.
Newton's Third Law
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
This book includes a set of features such as Analyzing-Multiple-Concept Problems, Check Your Understanding, Concepts & Calculations, and Concepts at a Glance. This helps the reader to first identify the physics concepts, then associate the appropriate mathematical equations, and finally to work out an algebraic solution.