A book resting on a table is in a state of equilibrium because the forces acting on it are balanced. Here's a breakdown of your options:
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The book's weight and the upward force the table exerts on the book have equal magnitude but opposing directions.
This is correct. The downward gravitational force (weight) of the book is balanced by the upward normal force exerted by the table. Since these two forces are equal in magnitude and opposite in direction, the net force acting on the book is zero, resulting in a state of equilibrium. -
The book and the table both have acceleration (due to gravity) of 9.8 m/s².
This statement is misleading. While the book does experience gravitational acceleration, it is not relevant to the state of equilibrium in this context. In equilibrium, the book is not accelerating; it is at rest. -
Gravity is a net force acting on the book in a downward direction.
While it's true that gravity is a force acting on the book, the term "net force" implies the result of all forces acting on the book. Since the upward normal force balances the downwards gravitational force, the net force is zero, which is key to the book being in equilibrium. -
The book and the table have the same weight.
This statement is incorrect. The book has a weight that depends on its mass and gravity, while the table’s weight is entirely separate and does not need to be equal to the book's weight for the book to be in equilibrium.
In summary, the primary reason the book is in equilibrium is the balance of forces: its weight is counteracted by the normal force from the table, leading to a net force of zero. Thus, the correct explanation is found in the first statement.
1 answer