The mercury density (at liquid state) is
[tex]\rho = 13.5 g/cm^3=13500 kg/m^3[/tex]
And we know that the pressure at the bottom of a column of fluid is given by (Stevin's law)
[tex]p=\rho g h[/tex]
where
[tex]\rho[/tex] is the liquid density
g is the gravitational acceleration
h is the height of the column of fluid
The pressure at the bottom of the beaker is [tex]p=26000 Pa[/tex], therefore we can re-arrange the previous equation to get the height of the column of mercury
[tex]h= \frac{p}{\rho g}= \frac{26000 Pa}{(13500 kg/m^3)(9.81 m/s^2)}=0.196m = 19.6 cm [/tex]
