Question

What length of the water column is equivalent to 0.76 m mercury column?

Answer 1

We know pressure exerted by a liquid column of height h, density p is
P = h x p x g.

The pressure exerted by the mercury column of height 76 cm.
Density of mercury = 13.6 g/cc = 1.36 x 10⁴kg/m³.
P_mercury = 0.76 x 1.36 x 10⁴ x 9.8 = 10.12 x 10⁴ Nm^-2.
Let the height of the water column = hm.
Density of water = 1g/cc= 10³ kg/m³.
P_water = h x 10³ x 9.8 = 9.8h x10³ Nm^-2.
Now put P_mercury = P_water

9.8 h x10³ = 10.12 x 10⁴

h = 10.12/9.8 = 10.34 m.

So, 10.34 m height of water column would exert the same pressure on its base as a 76 cm column of mercury.