Question

What is the gage pressure at the bottom of the lake?

What is the absolute pressure at the bottom of the lake?

Answer 1

`P_g=\rho_w.g.h` (gauge pressure)

`P_(abs)=P_(atm)+\rho_w.g.h` (absolute pressure)

Step-by-step explanation:

The gauge pressure is the pressure measured with reference to the atmospheric pressure where as the absolute pressure is the pressure measured including the atmospheric pressure taking absolute vacuum as the reference.

So when gauge measuring the pressure at the bottom of a lake the pressure only due to the water column above that point is measured which can be calculated as:

`P_g=\rho_w.g.h`

where:

`\rho_w=` density of water

`g=` acceleration due to gravity

`h=` height of the water column

Since the atmospheric pressure at the surface of the sea level is defined as the atmospheric pressure.

So, the absolute pressure:

`P_(abs)=P_(atm)+\rho_w.g.h`

where:

`P_(atm)=` the atmospheric pressure at the sea level