Question

what is moment of inertia

Answer 1

Moment of Inertia is a quantity defined for an object (or more specifically, a system of particles) on the basis of it's mass distribution. The way we use it is 'moment of inertia of an object/ a system of particles about an axis'.....
The formula for the moment of inertia of an a system consisting of discrete masses about an axis at a certain time is:
\[\sum_{}^{} mr ^{2}\], that is the sum of the value mr^2 of all the discrete masses, 'm' being the mass of the particle and 'r' being it's perpendicular distance from the line about which the moment of inertia is being calculated, at that point of time.
For continuous objects, an integral is used in place of summation..