Question

Differentiate between free and forced vibrations.

Distinguish between free vibrations and forced vibrations (Two points).

Answer 1

Sr.No	Free vibrations	Forced vibrations
1	Free vibrations are produced when a body is disturbed from its equilibrium position and released.	Forced vibrations are produced by an external periodic force of any frequency.
2	To start free vibrations only, the force is required initially.	Continuous external periodic force is required. If external periodic force is stopped, then forced vibrations also stop.
3	The frequency of free vibrations depends on the natural frequency.	The frequency of forced vibrations depends on the frequency of the external periodic force.
4	The energy of the body remains constant in the absence of friction, air resistance, etc. Due to damping forces, total energy decreases.	The energy of the body is maintained constant by the external periodic force.
5	The amplitude of vibrations decreases with time.	Amplitude is small but remains constant as long as an external periodic force acts on it.
6	Vibrations stop sooner or later depending on the damping force.	Vibrations stop as soon as external periodic force is stopped.