Why is a book resting on a table in a state of equilibrium?
A book resting on a table is in a state of equilibrium because all the forces acting on it are balanced. In general, equilibrium means that an object is either at rest or moving with a constant speed in a straight line.
In this case, there are two main forces acting on the book:
1. The force of gravity pulling the book downward.
2. The upward force exerted by the table (known as the normal force).
The force of gravity is acting downwards because of the book's weight. It is equal to the mass of the book multiplied by the acceleration due to gravity. The normal force exerted by the table is equal in magnitude but opposite in direction to the force of gravity.
When these two forces are equal, they cancel each other out, resulting in a net force of zero. As a consequence, the book remains at rest on the table, since there is no unbalanced force to accelerate or move it.
Additionally, the rotational equilibrium of the book is also maintained as the sum of the clockwise torques equals the sum of the counterclockwise torques acting on it. This ensures that the book does not rotate or tip over.
In summary, the book is in a state of equilibrium on the table because the forces acting on it are balanced both in terms of their overall magnitude and direction, as well as in terms of the torques they produce.