Question

To and fro motion of a particle about its mean position is called
A. Frequency
B. Amplitude
C. Vibration
D. Acceleration

Answer 1

Hint: The mean position of the particle is the equilibrium position of the particle. The particle is present at the equilibrium position at rest. Motion is the action of the particle by which it is moved.

Complete step-by-step answer:
To and fro motion of the object means forward and backward movement of the particle. Consider a pendulum of watch. This pendulum is allowed to move in a fixed path in forward and backward direction. This is to and fro motion of the pendulum.
The mechanical phenomenon that occurs by the to and fro motion of the particle is known as vibration of the particle. In vibration the particle oscillates about equilibrium position.
There are three types of vibrational motion:
i. Forced vibration
ii. Damped vibration
iii. Free vibration.

Thus, Option (C) is correct.

Note: Alternate method
Frequency is defined as the number of vibrations in one second. Thus, this is not to and fro motion of the particle.
Amplitude is defined as the maximum distance of the particle from the equilibrium position. Thus, this is not to and fro motion of the particle.
Acceleration is defined as the rate of change of velocity with respect to time. Thus, this is not to and fro motion of the particle.
Vibration of the particle is defined as to and fro of the particle from the mean position.