Q.
A light hollow cube of side length 10 cm and mass 10 g, is floating in water. It is pushed down and released to execute simple harmonic oscillations. The time period of oscillations is $y\pi\times10^{-2}$ s, where the value of $y$ is (Acceleration due to gravity, $g=10\ \mathrm{m/s^2}$, density of water $=10^3\ \mathrm{kg/m^3}$)
A) 6
B) 2
C) 4
D) 1
Explanation
[Solution by Dr. Abubacker] The restoring force is the extra buoyancy $\rho gAx$, so $\omega^2=\frac{\rho gA}m=\frac{10^3\times10\times10^{-2}}{10^{-2}}=10^4$, $\omega=100$ rad/s. $T=\frac{2\pi}{100}=2\pi\times10^{-2}$ s, so $y=2$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.