Question

A cube with a mass m= 20g floats on the surface of water. Each face of the cube is 3cm long. what is the distance between lower surface of the cube and surface of the water? (Surface tension of water = 70 $\times$ ${10}^3$ N/m)

• A. 3.31cm
• B. 4.31cm
• C. 2.31cm
• D. 1.31cm

Answer 1

The correct option is C

2.31cm

Down ward force = Buoyant force

mg+4Ta = $a^2$x$\rho$g

$\Rightarrow$x= $\frac{mg+4Ta}{a^2\rho g}$

= $\frac{20\times {10}^{-3}+4\times 70\times {10}^{-3}\times 3\times {10}^{-2}}{9\times {10}^{-4}\times {10}^3}\times 10$

= $\frac{.2+0.0084}{9}$ = $\frac{0.2084}{9}$

= 0.02315m

x=2.31 cm