Question

What are some examples of static equilibrium?

Answer 1

Hint: To find some examples of static equilibrium, we first need to understand the definition conditions of static equilibrium. A body is said to be in static equilibrium if it is in a state of equilibrium and also at rest. We shall see the condition of static equilibrium and then try to answer our question.

Complete step-by-step solution:
First of all, let us understand equilibrium of a body can be classified into two categories. These two categories are static equilibrium and dynamic equilibrium. Now, the conditions for a body to be in static equilibrium is:
(a) The summation of all the external forces acting on the body must be equal to zero. This statement is the first and foremost important criteria for any body to be in any type of equilibrium. This implies that the net acceleration of the body should be zero.
(b) The summation of all the torques due to all the forces acting on the body must be equal to zero.
(c) The body must be at rest at all times.
The examples of static equilibrium are:
(i) a book resting on a table
(ii) a car parked on a road
(iii) a boy standing still on the podium
(iv) a ball kept on the ground.
Hence, any non-moving stationary object can be considered to be in static equilibrium.

Note: In some cases, like when equal and opposite forces are applied on a stationary rod kept on a table, the net force on the rod becomes equal to zero but it gains some torque in the process. This state of rod will not be considered as an equilibrium state as it has some angular acceleration.