Finding modulus of rigidity G from torsion pendulum experiment

[queenstudy]

Homework Statement

i did my experiment on torsion pendulum and there is a graph that i am supposed to draw ( C as a function of 1/L) where C is the tosion constant and L the length of the wire after that they give me a formula C=1/32L *∏*G*a^4 where G is called the modulus of rigidity and a is the diameter of the wire my purpose is to find G

Homework Equations

1) i just want to know the expected result of G because i got 300 Pa??
2) how to find the uncertainty of G ?
3) the unit of G is Pa right??

The Attempt at a Solution

i did the graph where i am supposed to make the uncertainty rectangles but the graph didnt work out too much for me especially that i repeated the experiment several times and i have the same answers ( with a small difference) so any suggestions

 

[Spinnor]

It looks like yes to 3 but typical numbers for metal are 10's of giga Pa, 10E9 Pa see,

http://www.engineeringtoolbox.com/modulus-rigidity-d_946.html

from,

https://www.google.com/webhp?hl=en#...w.,cf.osb&fp=2ddf388403c0c5d8&biw=734&bih=439

For question 2 it looks like most error will come from a as it goes to the 4th power and it is most likely very small. What was a and to what fraction of an inch or mm did you measure, like wise for L.

I think your answer to 1 is way off, are your lengths in meters or mm? Pascals are Newtons per m^2.

 

[queenstudy]

so what i can see the number should be big