If a simple pendulum has significant amplitude (up to a factor of $1/e$ of original) only in the period between $t = 0\,\mathrm{s}$ to $t = \tau\,\mathrm{s}$, then $\tau$ may be called the average life of the pendulum. When the spherical bob of the pendulum suffers a retardation (due to viscous drag) proportional to its velocity, with $b$ as the constant of proportionality, the average life time of the pendulum is (assuming damping is small) in seconds: (1) $\dfrac{0.693}{b}$ (2) $b$ (3) $\dfrac{1}{b}$ (4) $\dfrac{2}{b}$
If a simple pendulum has significant amplitude (up to a factor of $1/e$ of original) only in the period between $t = 0\,\mathrm{s}$ to $t = \tau\,\mathrm{s}$, then $\tau$ may be called the average life of the pendulum. When the spherical bob of the pendulum suffers a retardation (due to viscous drag) proportional to its velocity, with $b$ as the constant of proportionality, the average life time of the pendulum is (assuming damping is small) in seconds:\\
(1) $\dfrac{0.693}{b}$\\
(2) $b$\\
(3) $\dfrac{1}{b}$\\
(4) $\dfrac{2}{b}$