Why is a book resting on a table in a state of equilibrium?
The book and the table have the same weight.
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The book and the table both have acceleration (due to gravity) of 9.8 m/s/s.
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.
All of these statements contribute to the book resting on the table in a state of equilibrium. In particular, the last statement explains that the force of gravity acting on the book is balanced by the upward force exerted by the table. This balance of forces results in no net force acting on the book, which means there is no acceleration or movement. Therefore, the book remains in a state of equilibrium.
Therefore, the book is in a state of equilibrium because the forces acting on it are balanced. The weight of the book pulls it downward, while the table exerts an equal and opposite upward force, resulting in no net force acting on the book. This balance of forces keeps the book in place, resting on the table without any motion.
To understand why the book is in a state of equilibrium when resting on a table, we need to consider the concept of forces and equilibrium.
When an object is at rest, it is said to be in a state of equilibrium. In this case, the book is at rest on the table. For an object to be in equilibrium, two conditions must be satisfied:
1. The net force acting on the object must be zero.
2. The net torque (rotational force) acting on the object must be zero (assuming there is no rotation involved).
Let's analyze these conditions in the context of the book on the table:
1. The net force: Gravity is the force acting on the book, pulling it downward towards the center of the Earth. This force is known as the weight of the book. Simultaneously, the table exerts an upward force on the book to support its weight.
Since the book is not accelerating vertically (it remains stationary), we can conclude that the magnitudes of the weight and the upward force from the table are equal. This means that while the weight pulls the book downward, the table's force cancels it out, resulting in a net force of zero on the book. Therefore, the first condition for equilibrium is met.
2. The net torque: Torque is the rotational force that tends to cause an object to rotate. To assess this condition, we need to consider the pivot point of the book. Assuming the book rests flat on the table, the pivot point would be the contact point between the book and the table.
Since the book is not rotating (it remains in a fixed position), we can conclude that the net torque acting on the book is also zero. This means that there is no rotational force trying to make the book spin, satisfying the second condition for equilibrium.
In conclusion, the book on the table is in a state of equilibrium because the net force acting on it is zero (due to the equal and opposite forces of gravity and the table) and the net torque acting on it is zero (as there is no rotational force present).