Question

What is the condition of equilibrium?

Answer 1

Here we have to tell the condition of equilibrium and there are two conditions of equilibrium. Where equilibrium is the condition of a system where neither its state of motion nor its internal energy state tends to change with time. In different subjects different definitions for equilibrium are present.

Complete step by step solution:
AS per the given problem we have two condition for a system to be in the state of equilibrium:
(i)The sum or we can say the resultant of all the external forces that are acting on a body must be equal to zero.
Mathematically we can say that,
$\sum\limits_{i = 1}^n {{F_i} = 0}$
Where, i is the number of force acting on a body and n is the total force that is acting.
We can expand it as,
${F_1} + {F_2} + {F_3} + ...............{F_n} = 0$
(ii)The second one says that the sum or resultant of all the external torques from external forces acting on an object must be equal to zero.
Mathematically we can say that,
$\sum\limits_{i = 1}^n {{\tau _i} = 0}$
Where, i is the number of force acting on a body and n is the total force that is acting.
We can expand it as,
${\tau _1} + {\tau _2} + {\tau _3} + ...............{\tau _n} = 0$
Now these above two conditions must simultaneously satisfy a body to maintain equilibrium.
Example for a body to be in equilibrium is a ball bearing balanced on the edge of a razor blade. It is balanced by the ball bearing because all the forces and torque acting on it is zero.

Note:
Remember that we can also define these two conditions as the body to be equilibrium, it should not experience any kind of acceleration neither linear nor angular so that both net force and the net torque acting on the body must be zero.