Question

what is the difference between moment of inertia and polar moment of inertia??

Answer 1

i.e. between I and J

Answer 2

http://en.wikipedia.org/wiki/Polar_moment_of_inertia

Answer 3

moment and polar inertia is something you can't really visualize. You have read about it and try to understand yourself. I would suggest read the textbook and apply the formula using tabular method to fully understand what inertia is.