The disc of a torsional pendulum has a moment of inertia of 0.05kgm^2 and is immersed in a viscous fluid. The shaft to which the disc is attatched has a 1cm diameter, is 30cm long and has a shear modulus of 40GN/(m^2). When the pendulum oscillates the amplitude of the first cycle is 6 gradians and the amplitude of the fourth cycle is 0.75 gradians. Calculate the following:
1- Logarithmic decrement
2- Damping coefficient
3- Damped natural frequency.