The amplitude of a damped oscillator decreases to 0.9 times its original magnitude in 5s. In another 10s it…

The amplitude of a damped oscillator decreases to 0.9 times its original magnitude in 5s. In another 10s it will decrease to α times its original magnitude, where α equals :
  1. 0.729
  2. 0.6
  3. 0.7
  4. 0.81

Solution

A=A0 e-bt2m

After 5 second

0.9 A 0 = A 0  e - b 5 2 m    ...... (i)

After 10 more second

A = A 0  e - b 1 5 2 m      ...... (ii)

From (i) and (ii)

A = 0.729 A 0

Asked in: JEE Main 2013 (07 Apr)

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