Electromagnetic Induction and Alternating Current 7 Question 7

7. The amplitude of a damped oscillator decreases to 0.9 times its original magnitude is $5 s$. In another $10 s$, it will decrease to $\alpha$ times its original magnitude, where $\alpha$ equals $\quad$ (2013 Main)

(a) 0.7

(b) 0.81

(c) 0.729

(d) 0.6

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Answer:

Correct Answer: 7. (c)

Solution:

  1. Amplitude decreases exponentially. In $5 s$, it remains 0.9 times. Therefore, in total $15 s$ it will remains $(0.9)(0.9)$ $(0.9)=0.729$ times its original value.


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