The force of gravity pulling downward and the force of the table pushing upwards on the book are of equal magnitude and opposite directions. These two forces balance each other. Yet there is no force present to balance the force of friction. As the book moves to the right, friction acts to the left to slow the book down. The book is not at equilibrium and subsequently accelerates.
Unbalanced forces cause accelerations .
To determine if the forces acting upon an object is balanced or unbalanced, an analysis must first be conducted to determine what forces are acting upon the object and in what direction. If two individual forces are of equal magnitude and opposite direction, then the forces are said to be balanced. Such analyses are discussed in Lesson 2 of this unit and applied in Lesson 3 . Upon encountering the haystack, the box of shingles encounters a 50.0 N upward restraining force. Use this description to answer the following questions.