The amplitudes of a damped harmonic oscillator after 2 and 4 seconds are $A_1$ and $A_2$ respectively. If…

The amplitudes of a damped harmonic oscillator after 2 and 4 seconds are $A_1$ and $A_2$ respectively. If the initial amplitude of the oscillator is $\mathrm{A}_0$, then
  1. $\mathrm{A}_1=\sqrt{\mathrm{A}_0 \mathrm{~A}_2}$
  2. $\mathrm{A}_2=\sqrt{\mathrm{A}_0 \mathrm{~A}_1}$
  3. $\mathrm{A}_0=\sqrt{\mathrm{A}_1 \mathrm{~A}_2}$
  4. $\mathrm{A}_1=\frac{\mathrm{A}_0+\mathrm{A}_2}{2}$

Solution

In damping harmonic oscillator, amplitude $ \begin{aligned} & A=A_0 e^{-b t} \\ & \therefore A_1=A_0 e^{-b \times 2} \Rightarrow \frac{A_1}{A_0}=e^{-2 b} \end{aligned} $ And $ \begin{aligned} & A_2=A_0 e^{-b \times 4} \Rightarrow \frac{A_2}{A_0}=e^{-4 b}=\left(e^{-2 b}\right)^2=\left(\frac{A_1}{A_0}\right)^2 \\ & \text { or, } \frac{A_2}{A_0}=\left(\frac{A_1}{A_0}\right)^2=\frac{A_1^2}{A_0^2} \text { or, } \frac{A_2}{A_1^2}=\frac{1}{A_0} \therefore A_1=\sqrt{A_0 A_2} \end{aligned} $

Asked in: AP EAMCET 2023 (15 May Shift 1)

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