What is the radius of the biggest aluminium coin of thickness t and density `rho`, which will still be able to that on the water surface of surface tension S ?

Options

A. `(4S)/(3rho g t)`
B. `(3S)/(4rho g t)`
C. `(2S)/(rho g t)`
D. `(S)/(rho g t)`

Answer

C

Explanation

Let R be the radius of the biggest aluminium coin which will be supported on the surface of water due to surface tension.
Then `mg = S xx 2pi R`
or `pi R^(2) t rho g = S xx 2pi R rArr R = 2S//rho g t`