A cube with a mass `= 20 g` wettable water floats on the surface of water. Each face of the cube is `alpha = 3 cm` long. Surface tension of water is `70 dyn//cm`. The distance of the lower face of the cube from the surface of water is (`g= 980 cm s^(-12)`)

Options

A. `2.3cm`
B. `4.6cm`
C. `9.7cm`
D. `12.7cm`

Answer

A

Explanation

If `y` is the required distance, then
`a^(2)yrhog=mg+4asigma`
or `y=(mgxx4asigma)/(a^(2)rhog)=(20xx980+4xx3xx70)/(3xx3xx1xx980)cm=2.3cm`