Q.
The amplitude of a damped oscillator decreases to 0.9 times its original magnitude is 5s. In another 10s it will decrease to
a times its original magnitude, where α equals
Amplitude decreases exponentially. In 5 s it remains
0.9 times. Therefore in total 15 s it will remains (0.9) (0.9)
Answer is 4. (0.9) = 0.729 times its original value.