Torsional Pendulum Questions and Answers for Viva

Answer-1: A body suspended from a rigid support by means of a long and thin elastic wire is called torsional pendulum.

Answer-2: This is of simple harmonic oscillation type.

Answer-3: It depends upon:
1. Moment of inertia of the body
2. Rigidity of wire i.e., length, radius and material of the wire.

Answer-4: As fluids do not have a shape of their own, hence they do not posses rigidity. Hence there is no question of determining.

Answer-5: Time taken for one complete oscillation.

Answer-6: When tangential surface forces are applied on a body ,the successive layers of the material are moved or sheared. This type of strain is called shearing strain. ?the ratio of tangential stress to shearing strain is called Rigidity of modulus? i.e.
Rigidity of modulus = Tangential Stress / shearing Strain
Tangential Stress = Force/ Area
Shearing Strain = θ

Answer-7: It is the measure of the inertia of a body in rotator motion. It depends upon the axis of rotation ,mass of the body and also on the distribution of the mass about the axis.

Answer-8: The disk is making oscillations around a vertical axis passing through its centre of mass and hence the arrangement is called a torsional pendulum.

Answer-9: In a simple pendulumthe simple harmonic motion is due to the restoring force which is the component of the weight of the bob. In a torsional pendulum the simple harmonic motion is due to restoring couple araising out of torsion and shearing strain.

Answer-10: A body is said to have a S.H.M. ,if its acceleration is always directed towards a fixed point on its path and is proportional to its displacement from the fixed point.

Answer-11: It is the ratio of longitudinal stress to the longitudinal strain.

Answer-12: If the air friction is neglected, restoring force on the bob = mg Sin θ.

Answer-13: Zero, since at mean position the weight of the bob is perfectly balanced by the tension (T) in the string.