For the situation shown, the tissues in the elephant’s abdomen are at a gauge pressure of 150 mm Hg. This pressure corresponds to what distance below the surface of a lake? (a) 1.5 m;(b) 2.0 m; (c) 3.0 m; (d) 15 m.

The gauge pressure is, P = 150 mm Hg.

1atm = 760 mm Hg

An item submerged in fluid, or the surface of a closed container, is subject to fluid pressure, which is defined as the force applied acting on that object.

A positive gauge pressure indicates a pressure higher than or equal to or greater than or equal to or greater than or equal to or greater than or equal to or greater than atmospheric pressure. The pressure can be given as, $P=\rho gh$ … (i)

$\because 1atm=760mm$Hg

The pressure can be given as,

$P=\left(\frac{150\mathrm{mm}}{750\mathrm{mm}}\right)P_{atm}$

Using equation (i), the expression can be given as,

role="math" localid="1668056822739" $h=\frac{P}{\rho g}$

Substitute the values in the above equation.

$\begin{array}{r}h=\frac{\left(\frac{150\mathrm{mm}}{760\mathrm{mm}}\right)\left(1.01\times {10}^5\mathrm{Pa}\right)}{\left(1000\mathrm{kg}/{\mathrm{m}}^3\right)\left(9.80\mathrm{m}/{\mathrm{s}}^2\right)}\\ =2.0\mathrm{m}\end{array}$

Hence, the distance below the surface of lake is 2.0 m. And the correct option is (b).