Elasticity

Property of material of body by virtue of which the body acquires its original shape and size after removal of deforming force.

Stress: the restoring force per unit area set up inside the body subjected to deforming force is called stress.

strain: the relative change in dimension or shape of body which is subjected to stress is called strain. It is measure of ration of change in length to the original length, change in volume to the original volume.

Elastic law

Hooke's Law: stress is proportional to strain.

E=stress/strain, elastic constant.

Elastic constant is of three type:

Young modulus: Longitudinal stress/Longitudinal strain

Bulk Modulus: Volume stress/Volume strain

Rigidity modulus: Tangential stress/shear strain.

Simple Harmonic Motion

If a particle repeat its  motion about a fixed point after a regular time interval in such way that any moment the acceleration of particle is directly proportional to its displacement from the fixed point at that moment.

Characteristics of SHM:

When particle passes through mean position:

• No force acts on particle
• Acceleration of particle is zero
• Velocity is maximum
• kinetic energy is maximum
• potential energy is zero

When particle passes through extreme position:

• Acceleration of particle is maximum
• restoring force acting of particle is maximum
• velocity of particle is zero
• Kinetic energy is zero
• potential energy is maximum.

Simple Pendulum:

T = 2π √R/2g.