Some question about the Maxwell needle method experiment.

[Outrageous]

Homework Statement

1)How do we obtain the formula of torsional rigidity ,c=∏nr^4/(2L) ?From experiment? then how do the ∏ come from? How do they know the n here is the rigidity modulus? Why it is not the young's modulus?
2)Is Maxwell needle method same as the torsional pendulum? Both can be used to calculate rigidity modulus of a wire. Which is better ? Why?

Homework Equations

The Attempt at a Solution

http://scienceworld.wolfram.com/physics/TorsionalPendulum.html
I have tried to google and get some reference book but nothing about these .
Guide will do . At least please tell me ways to get torsional rigidity. Just the name of experiment will do. Thank you

 

[Chhavinath sahu]

What is the standerd value of modulus of regidity of a maxwell's needle