A cone with half the density of water is floating in water as shown. It is depressed down by a small distance \( \delta \ll H \) and released. The frequency of SHM of the cone is:
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Floating body SHM uses buoyancy-based restoring force and mass of displaced liquid.
The restoring force is due to buoyancy and acts as effective restoring force in SHM. Using geometry and Archimedes’ principle, the effective spring constant \( k \) is proportional to the displaced volume gradient. After deriving and simplifying, the frequency of SHM comes out to be:
\[
f = \frac{1}{2\pi} \sqrt{\frac{6g}{H} \cdot \frac{1}{4\sqrt{3}}}
\]