Static is the branch of mechanics which deals with the study of bodies at rest under a number of forces, the equilibrium, conditions of equilibrium, types of equilibrium, torque etc.
A body is said to be in equilibrium if it is at rest or moving with uniform velocity.
In other words if the linear and angular acceleration of a body are zero, the body is said to be in equilibrium.
Or we can say that when two or more forces act on a body such that their resultant or combining effect on the body is zero and the body retains its state of rest or of uniform motion then the body is said to be in equilibrium.
A book lies on the table, suspended bodies, all stationary bodies, jump by using parachute.
Types of equilibrium
With respect to the state of a body, equilibrium may be divided into two categories:
- Static equilibrium.
- Dynamic equilibrium.
1. Static equilibrium
If the combined effect of all the forces acting on a body is zero and the body is in the state of rest then its equilibrium is termed as static equilibrium. For example: All stationary bodies.
2. Dynamic equilibrium
When a body is in state of uniform motion and the resultant of all forces acting upon it is zero then it is said to be in dynamic equilibrium. For example: Jump by using parachute.
Conditions of equilibrium
There are two conditions of equilibrium are as follows:
First condition of equilibrium
The first condition of equilibrium stated as follows:
To maintain transitional equilibrium in a body the vector sum of all the forces acting on the body is equal to zero. In other words we can say that to maintain equilibrium the sum of all the forces acting along X-axis is zero and the sum of all the forces acting along Y-axis is zero.
Second condition of equilibrium
The second condition of equilibrium stated as follows:
A body will be in rotational equilibrium when the vector sum of all the torques acting on it is zero.