Forced Vibrations

A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap is opened and the water level gradually falls. It is observed that the sound becomes the loudest for a particular length of the air column. What is the name of the phenomenon taking place when this happens? Why does the sound become the loudest?

A bucket kept under a running tap is getting filled with water. A person sitting at a distance is able to get an idea when the bucket is about to be filled.
(i) What change takes place in the sound to give this idea?
(ii) What causes the change in the sound?

The diagram above shows a wire stretched over a sonometer. Stems of two vibrating tuning forks A and Bare touched to the wooden box of the sonometer. It is observed that the paper rider (a small piece of paper folded at the centre) present on the wire flies off when the stem of vibrating tuning fork B is touched to the wooden box but the paper just vibrates when the stem of vibrating tuning fork A is touched to the wooden box.

1) Name the phenomenon when the paper rider just vibrates.

2) Name the phenomenon when the paper rider flies off.

3) Why does the paper rider fly off when the stem of tuning fork B is touched to the box?

What do you understand by free vibrations of a body? Draw a displacement-time graph to represent them. Given one example.

Give two examples of forced vibrations.

Distinguish between the free (or natural) and forced vibrations.

What do you understand by free (or natural) vibrations?

Give one example to illustrate forced vibrations.