Question

A blade, fixed at one end, is made to vibrate by pressing its other end and then releasing it. State one way in which the frequency of vibrations of the blade can be lowered.

Answer 1

The vibration that takes place under the excitation of external forces is called forced vibration. If excitation is harmonic, the system is forced to vibrate at excitation frequency. If the frequency of excitation coincide with one of the natural frequencies of the system, a condition of resonance is encountered and dangerously large oscillations may result, which results in failure of major structures, that is, bridges, buildings, airplane wings etc.
In this case, when the blade is excited, the blade vibrates vigorously. The frequency of the vibrating body depends on factors like length of the vibrating body, mass of the vibrating body, tension in the vibrating body and mode of vibration.
Hence, the frequency of the blade can be lowered by increasing the length of the blade or by sticking a small weight on the blade at its free end.