## Procedure: (for performing in lab)

####

### PART 1: Determination of Rigidity modulus using Torsion pendulum alone

- The radius of the suspension wire is measured using a screw gauge.
- The length of the suspension wire is adjusted to suitable values like 0.3m,0.4m,0.5m,.....0.9m,1m etc.
- The disc is set in oscillation.Find the time for 20 oscillations twice and determine the mean period of oscillation ' T
_{0 }'.
- Calculate moment of inertia of the disc using the expression, I = (1/2)MR
^{2}_{.}
- Determine the rigidity modulus from the given mathematical expression.

### PART 2: Determination of rigidity modulus and moment of inertia using torsion pendulum with identical masses

- The radius of the suspension wire is measured using a screw gauge.
- The length of the suspension wire is adjusted to suitable values like 0.3m,0.4m,0.5m,.....0.9m,1m etc.
- The disc is set in oscillation.Find the time for 20 oscillations twice and determine the mean period of oscillation ' T
_{0 }'.
- The two identical masses are placed symmetrically on either side of the suspension wire as close as possible to the centre of the disc, and measure d
_{1} which is the distance between the centres of the disc and one of the identical masses.
- Find the time for 20 oscillations twice and determine the mean period of oscillation ' T
_{1 }'.
- The two identical masses are placed symmetrically on either side of the suspension wire as far as possible to the centre of the disc, and measure d
_{2} which is the distance between the centres of the disc and one of the identical masses.
- Find the time for 20 oscillations twice and determine the mean period of oscillation ' T
_{2 }'.
- Find the moment of inertia of the disc and rigidity modulus of the suspension wire using the given formulae.

#### **Note: For the same variables of length,mass, etc. the data from part 1 can be used for the Part 2 procedure.**

##

## Observations:

Length of the suspension wire=................m

Radius of the suspension wire=..............m

Mass of each identical masses=.............kg

d_{1}=...........m

d_{2}=...........m

For Part 1:

For Part 2:

##

## Calculations:

T_{0 }= ........s

T_{1} = .........s

T_{2 }= .........s

### For Part 1:

### For Part:2

Moment of inertia of the given disc,

And the rigidity modulus of the suspension wire,