Asked by Jenna
Within a book on a desk there are billions of forces pushing and pulling on all the molecules. Why is it that these forces never by chance add up to a net force in one direction, causing the book to accelerate "spontaneously" across the desk?
Answers
Answered by
drwls
Think about Newton's third law. All of the internal forces consist of equal and pooosite pairs, and the vector sum is zero.