Driving force from buzzer for jacket of length L

[Callumnc1]

Homework Statement:

Please see below

Relevant Equations:

Please see below

For this problem,

How do we tell when the buzzer vibrates during the cycle to provide the driving force?

Many thanks!

 

[haruspex]

How do we tell when the buzzer vibrates during the cycle to provide the driving force?

It's an example of resonance. https://en.wikipedia.org/wiki/Resonance.
Because there are losses in the swinging cloth, it will always be a bit behind the source of vibration (phase lag). As a result, the impetus from the source is reinforcing.

 

[Callumnc1]

It's an example of resonance. https://en.wikipedia.org/wiki/Resonance.
Because there are losses in the swinging cloth, it will always be a bit behind the source of vibration (phase lag). As a result, the impetus from the source is reinforcing.

Thank you for your reply @haruspex !