Question

There is small hole in a hollow sphere. The water enters in it is taken to a depth of $40cm$ under water. The surface tension of water is $0.07N/m$ . The diameter of hole is :

• A. $7mm$
• B. $0.07mm$
• C. $0.0007mm$
• D. $0.7m$

Answer 1

The correct option is B $0.07mm$

Since, under equilibrium condition, the pressure exerted by water would be equal to the excess pressure inside the bubble.

It can be written as,

$\frac{2T}{r}=h\rho g$

$\frac{2\times 0.07}{r}=40\times {10}^{-2}\times {10}^3\times 9.81$

$r=3.57\times {10}^{-5}m$

The diameter of the hole is given as,

$d=2r$

$d=2\times 3.57\times {10}^{-5}$

$=7.135\times {10}^{-5}m$

Thus, the diameter of the hole is $0.07mm$.