The rear view mirror of a motorbike starts vibrating violently at a particular speed of the motorbike.
$(a)$ Why does this happen?
$(b)$ What is the name of the phenomenon taking place?
$(c)$ What could be done to stop the violent vibration?

(N/A) This happens when the frequency of vibration produced by the engine of the motorbike becomes equal to the natural frequency of the rear view mirror.
$(b)$ The name of this phenomenon is resonance.
$(c)$ The speed of the motorbike should be changed,which will alter the frequency of vibration of the engine,thereby stopping the resonance condition.