Why is a book resting on a table in a state of equilibrium?
Gravity is a net force acting on the book in a downward direction.
The book's weight and the upward force the table exerts on the book have equal magnitude but opposing directions.
The book and the both have acceleration (due to gravity) of 9.8 m/s/s.
The book and the table have the same weight
magnitude but opposite directions.
The book is at rest, meaning its velocity is zero.
Since the book is not moving and there is no unbalanced force acting on it, the book is in a state of equilibrium.