A 200 g oscillator in a vacuum chamber has a frequency of 3.5 Hz. When air is admitted, the oscillation decreases to 60% of its initial amplitude in 40 s. How many oscillations will have been completed when the amplitude is 20% of its
initial value?

Question

A 200 g oscillator in a vacuum chamber has a frequency of 3.5 Hz. When air is admitted, the oscillation decreases to 60% of its initial amplitude in 40 s. How many oscillations will have been completed when the amplitude is 20% of its 
initial value?

lncognlto · Answer

I know the formula for damped oscillations is$$X_{\max} (t) = Ae ^{\frac{ -1 }{ \tau }}$$, but after that, I am lost. :s

lncognlto · Answer

@wolfe8 @gyanu