Solution:
a) When the teacher comes toward the student the sound
passing through the unit area increases with a decrease in the distance, due to which the student sitting on a bench feels the increasing pitch of a sound as the teacher
approaches to him while explaining a lesson.
b)
Given:
Let V be the velocity of sound in air.
Frequency of Source (fo) = 90Hz
Velocity of Source of Sound (vs) = $\frac{1}{{10}}V$
Since the source is moving toward the stationary observer
Apparent Frequency (f’) = $\frac{V}{{V - {V_s}}}{f_o}$
$\begin{array}{l} = \frac{V}{{V - \frac{1}{{10}}V}} \times
90\\ = 100Hz\end{array}$
c)
Tuning a guitar involves adjusting the tension of the
strings, which directly affects the pitch. Tightening the strings increases the
pitch while loosening the strings decreases the pitch. The screw at the end of
the tuning peg on a guitar is used to rotate the gear mechanism within the
tuning machine, which changes the tension in the string. This is based on the
principles of mechanics and the relationship between tension and pitch in
vibrating strings.
d)
To create a transverse wave in the spring, the spring needs to
be fixed at one end, and the other end needs to be moved perpendicular to the
direction of the spring. This can be done by attaching the spring to a wall or
a fixed object and then pulling or pushing the free end of the spring sideways.
This creates a disturbance in the spring, which travels along the length of the
spring as a transverse wave. The motion of the spring's particles is
perpendicular to the direction of wave propagation, creating the transverse
wave. The properties of the wave, such as frequency and wavelength, depending on
the properties of the spring, such as its mass, length, and tension.