A classical mechanics problem by Pratik Shastri

Classical Mechanics Level 4

A pendulum oscillates, immersed in water. The mass of the bob is $250 \ g$ , length of the string is $30 \ cm$ , the radius of the bob is $2 \ cm$ and density of water $\rho_w$ is $1000 \ kg/m^3$ .

Calculate the time period of its oscillations (in seconds), considering its amplitude to be small.

$\textbf{Assumptions}$

$\bullet$ Take $g=9.8 \ m/s^2$

$\bullet$ Ignore drag forces.