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AP EAMCET · PHYSICS · Oscillations

The displacement of a damped harmonic oscillator is given by \(x(\mathrm{t})=\mathrm{e}^{-0.1 \mathrm{t}} \cos (10 \pi \mathrm{t}+\varphi)\). Here \(\mathrm{t}\) is in seconds. The time taken for its amplitude of vibration to drop to half of its initial value is close to:

  1. A \(27 \mathrm{~s}\)
  2. B \(4 \mathrm{~s}\)
  3. C \(13 \mathrm{~s}\)
  4. D \(7 \mathrm{~s}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(7 \mathrm{~s}\)

Step-by-step Solution

Detailed explanation

Amplitude \(A=A_0 e^{-k t}\) From given condition, \(\frac{A_0}{2}=A_0 e^{-0.1 \times t}\) \[ \begin{aligned} & \Rightarrow \ln 2=0.1 \times t \\ & t=\frac{\ln 2}{0.1}=\frac{0.693}{0.10}=6.935 \approx 7 \mathrm{~s} \end{aligned} \]
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