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JEE Mains · Physics · STD 11 - Oscillations
- JEE Mains 2015
- Medium
- MCQ
A pendulum with time period of \(1\, s\) is losing energy due to damping. At certain time its energy is \(45\, J\). If after completing \(15\,oscillations\) , its energy has become \(15\, J\), its damping constant (in \(s^{-1}\) ) is
Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) \(\frac{1}{{15}}\ln \,3\)
Step-by-step Solution
Detailed explanation
As we know, \(E=E_{0} e^{-\frac{b t}{m}}\)
\(15=45 e^{-\frac{b 15}{m}}\)
[As no. of oscillations \(=15 \text { so } t=15 \mathrm{sec}]\)
\(\frac{1}{3}=e^{-\frac{b 15}{m}}\)
Taking log on both sides
\(\frac{b}{m}=\frac{1}{15} \ell \mathrm{n} 3\)
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