Q: When a block of iron floats in mercury at 0°C, a fraction k_{1} of its volume is submerged, while at the temperature 60°C, a fraction k_{2} is seen to be submerged. If the coefficient of volume expansion of iron is γ_{Fe} and that of mercury is γ_{Hg}, then the ratio k_{1}/k_{2} can be expressed as

(a) $ \displaystyle \frac{1 + 60 \gamma_Fe}{1 + 60 \gamma_Hg} $

(b) $ \displaystyle \frac{1 – 60 \gamma_Fe}{1 + 60 \gamma_Hg} $

(c) $\displaystyle \frac{1 + 60 \gamma_Fe}{1 – 60 \gamma_Hg} $

(d) $ \displaystyle \frac{1 + 60 \gamma_Hg}{1 + 60 \gamma_Fe} $

**Click to See Answer : **

$ \displaystyle \frac{k_1}{k_2} = \frac{\rho_{60}}{\rho_0}.\frac{V_{60}}{V_0} $

$ \displaystyle \frac{k_1}{k_2} = \frac{\rho_0 /(1+\gamma_{Hg} \times 60)}{\rho_0} \frac{V_0(1+\gamma_{Fe}\times 60)}{V_0} $

$ \displaystyle \frac{k_1}{k_2} = \frac{1+60 \gamma_{Fe}}{1+60 \gamma_{Hg}} $