Question

A scooter waiting on a signal has its mirror vibrating violently. Why?

Answer 1

Resonance:

1. It is a kind of vibration of large amplitude in a mechanical or electrical system caused by a relatively small periodic stimulus of the same or nearly the same period as the natural vibration period of the system.
2. Pushing a person in a swing is a general example of resonance.
3. The swing which is loaded, a pendulum, has its own natural frequency of oscillation, its resonant frequency, and resists being pushed at a faster or slower rate.
4. The main reason for scooter vibration is because of resonance.
5. When a body is subjected to forced vibration with a frequency that equals to or an integral multiple of the natural frequency of the body, the body vibrates with large amplitude violently.
6. The mirror has its own natural frequency, which may be equal to or multiple of the frequency of the engine of the scooter (frequency of forced vibration)
7. Hence it is vibrating violently. The rider should switch off the engine or change the speed of the scooter.

Thus, A scooter waiting on a signal has its mirror vibrating violently because of resonance.