Question

When a body is undergoing undamped vibration, the physical quantity that remains constant is
A) Amplitude
B) Velocity
C) Acceleration
D) Phase

Answer 1

It is directly related to the oscillations. In wave optics we have seen that a string attached to a place keeps on oscillating until it has energy to work. Undamped means the energy will not perish or end and amplitude directly depends on it.

Complete step-by-step answer:
Oscillation has vast applications in physics. It is important to know about oscillation before answering the question. A single swing or movement in one direction of an oscillating body. fluctuation between beliefs, opinions, conditions, etc. Physics. an effect expressible as a quantity that repeatedly and regularly fluctuates above and below some mean value, as the pressure of a sound wave or the voltage of an alternating current.
Now the question asks for the damped oscillation. It involves the damped harmonic motion.

DAMPED SIMPLE HARMONIC MOTION:- Motion in which amplitude of the oscillating body reduces and eventually comes to its mean position. Dissipating forces cause damping. Consider a pendulum which is oscillating. After some time we can observe that its displacement starts decreasing and finally it comes to rest.
The equation of Simple Harmonic Motion is (S.H.M) X=A Sin $\left( {\omega t + \phi } \right)$ here, X is the displacement and $\phi$ is the phase and A is the amplitude.
The amplitude directly depends on the energy of the system. If the system of oscillatory objects starts slowing down the amplitude itself starts decreasing and vice versa.
In damped oscillation the energy remains constant and hence the amplitude also remains constant.

Hence, option A is the correct answer.

Additional Information:
Damping oscillation: A damped oscillation means an oscillation that fades away with time. Examples:
- A swinging pendulum
- A weight on a spring

Note: Damping, in physics, restraining of vibratory motion, such as mechanical oscillations, noise, and alternating electric currents, by dissipation of energy. Unless a child keeps pumping a swing, its motion dies down because of damping. Shock absorbers in automobiles and carpet pads are examples of damping devices.