Question

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

Answer 1

Hint: here, the figure shows a sonometer, therefore, we will first define the sonometer. Also, we will define the tuning forks. When a tuning fork is touched with a wooden box, the wire starts vibrating. The fly off of the paper will depend on the frequency and the amplitude of the wire.

Complete step by step answer:
The figure above shows a sonometer. A sonometer is a device that consists of a hollow rectangular wooden box in which a uniform wire is attached at one end. The one end of the wire is attached to the knife-edge which goes over a pulley. A weight is attached to the other end of the wire. A sonometer is used to verify the laws of vibration and also to determine the frequency of the tuning fork.
Also, a tuning fork is defined as an acoustic resonator which is in the form of a two-pronged fork and these prongs are in a U-shape and made up of elastic metals (steel). The main reason for using a fork shape is that it provides a pure tone.
When we place a tuning fork A on the wooden box, the paper rider does not flow but it vibrates due to the vibration of the wire. But when the tuning fork B is touched with a wooden box, the frequency of the vibrating wire will match with the frequency of the tuning fork increasing the amplitude of the vibration of the wire, therefore, the paper will flow off. This process of increase in amplitude is known as resonance.
Therefore, when the stem of tuning fork B is touched to the box the piper rider flies off due to the resonance.

Note:
The example above shows the concept of forced oscillations. Resonance is particularly a case of forced oscillations.
When there will a large difference in the frequency of the system and the external force then forced oscillation will be limitless.
But when the frequency of the system will be the same as that of the external force, it is called resonance.