Question

A cube of side $a$ and mass $m$ just floats on the surface of water as shown in the figure. The surface tension and density of water are $T$ and ${\rho }_w$, respectively. If angle of contact between cube and water surface is zero, find the distance $h$ (in metres) between the lower face of cube and surface of the water.
(Take $m=1kg,g=10m/s^2,aT=\frac{10}{4}unit$ and ${\rho }_w{a}^{2}g=10unit)$.

Answer 1

$Mg+F_{ST}=B$
$mg+4AT=a^{2}h{\rho }_{w}g$
$10+4\times \frac{10}{4}=10h$
$h=2m$.