Question

A simple pendulum with a solid metal bob has a period T. What will be the period of the same pendulum if it is made to oscillate in a non-viscous liquid of density one-tenth of the metal of the bob?

Answer 1

$g_e=g-\frac{Uptrust}{mass}$
$=g-\frac{v\left(\delta /10\right)g}{v\delta }$
$=\frac{9}{10}g$
$T^{\prime }=2\pi \sqrt{\frac{l}{g_e}}=2\pi \sqrt{\frac{10}{9}\left(\frac{l}{g}\right)}$
$=\left(\sqrt{\frac{10}{9}}\right)T$