Question

The example of forced vibration is
$\left( a \right)$ Resonance
$\left( b \right)$ Beats
$\left( c \right)$ Interference
$\left( d \right)$ Diffraction

Answer 1

Hint: Vibrations which are induced by some external agent result in a mechanical device generating disturbances. Interference refers to wave superposition so this possibility is removed immediately. Diffraction is a bending effect of light from an object's sharp edges, which has little to do with vibrations. Thus the potential answer can only be resonance or beat. Think accordingly of what suits best in getting the answer.

Complete step-by-step answer:
Induced vibration is when an opposing force or motion is applied to a mechanical device, e.g. when a washing machine shakes due to an unbalance. Forced vibration is a form of vibration, where a force is applied repeatedly to a mechanical device.
Forced Resonance & Vibrations. Free vibrations are oscillations, in which over time the total energy stays the same. Which means vibration rate remains the same.
When an object is forced to vibrate at its natural frequency, there will be resonance, and you will detect vibrations with large amplitudes.
When the frequencies of two objects are matched i.e. super impose each other resonance occur, these resonances are very dangerous to the objects because at this resonance other objects continue vibrating which leads to the damage of the object.
So that's the response they need.
Thus choice (A) is the appropriate answer.

Note:Resonance is a phenomenon in which an external vibration or external vibration system forces another system to vibrate more amplitudinally than the initial system. If 2 identical waves of sound repeat variations due to the effects of crust and rough waves, these repeated variations can be detected in sound wave amplitude and are called beats.