Oscillations in many devices such as musical instruments are desirable. However, many oscillations, such as those caused by winds or earthquakes, can be very destructive.

$($a$)$

Define what is meant by resonant frequency, forced frequency, and mechanical resonance. Give an example of each.

$($b$)$

Give an example of a structure or machine in which mechanical resonance may be used to advantage. Describe how mechanical resonance is used in this device.

$($c$)$

Give an example or situation in which oscillations are undesirable. Describe what scientists and engineers can do to eliminate or reduce the effects of unwanted oscillations.