Question

what is the two difference between mass and moment of inertia

Answer 1

Moment of Inertia in a way shows/depicts the mass distribution in a body.

For example,

Moment of Inertia of a rod held from the end is M*L^2/3 and M*L^2/12 through an axis passing from its middle point.

Since the former Moment of Inertia is greater in magnitude, it shows that you need a greater torque to rotate it with the same angular acceleration.

More torque means more amount of work is to be done to rotate it with the same amount of angular displacement.

Now since the mass distribution in both the cases of the rod is different about their respective axis, their corresponding Moment of Inertia changes and hence everything related to it.

But Inertia means just the state of the body, whether it is in motion or at rest.

Answer 2

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Momentum, on the other hand, is the product of an object's mass and velocity, and is sometimes referred to as “mass in motion.” While a change in shape—the distance of mass from the axis of rotation—will change a system's inertia, the momentum of a system cannot be changed unless an external force acts on it.


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FIRST : "Mass" 

Mass is the amount of matter contained in a body >> Measured in Kg (kilogram) 

SECOND : moment of inertia. 

Moment of intertia is a property of area that's used in mechanics calculations. There's two : 

1) mass moment of inertia : equivalent to mass times square the distance to the centre of mass. 

I = m * (r^2) 

measured in ( Kg.m^2) 

2) Area moment of inertia : equivalent to area times square the distance to the centre of shape. 

J = A * (r^2) 

measured in ( m^4)