Question

Differentiate between the forced and resonant vibrations.

Answer 1

When a periodically varying force is applied on an object, the object vibrates in accordance to the frequency of applied force. The frequency of vibration of the object is the same as the frequency of the applied force. This is called forced vibration.
When the force is removed, the object will not vibrate with this frequency, but it will vibrate with a frequency peculiar to the object called natural frequency, every object has its own natural frequency.
Thus to make a body to vibrate with its natural frequency, we apply some varying force and remove that force. On removing the force the object will vibrate with its natural frequency. However, due to damping eventually the vibration will cease after certain time.
Suppose that the frequency of the applied force coincides with the natural frequency, in other words if the frequency of the forced vibration coincides with the natural frequency of the object, the amplitude of vibration is the maximum and this called resonance.