MCQ
A sphere of relative density $\sigma$ and diameter $D$ has concentric cavity of diameter $d$. The ratio of $\frac{D}{d}$, if it just floats on water in a tank is:
- ✓$\left(\frac{\sigma}{\sigma-1}\right)^{\frac{1}{3}}$
- B$\left(\frac{\sigma+1}{\sigma-1}\right)^{\frac{1}{3}}$
- C$\left(\frac{\sigma-1}{\sigma}\right)^{\frac{1}{3}}$
- D$\left(\frac{\sigma-2}{\sigma+2}\right)^{\frac{1}{3}}$

