Question

What is the pressure of the gas in this mercury manometer if h = 63 mm and atmospheric pressure is 773 mmhg?

Answer 1

We can find the gas pressure by using a simple proportion.

In fact, if the pressure of the gas was equal to the atmospheric pressure:

`p_a = 1.01 \cdot 10^5 Pa`
we know that the height in the mercury manometer would have been

`h_a = 773 mm`

Therefore, if the heigth in the mercury manometer is

`h=63 mm`
Then the pressure of the gas is given by the following proportion

`h_a : p_a = h: p`
From which we find

`p= (h p_a)/(h_a)= ((63 mm)(1.01 \cdot 10^5 Pa))/(773 mm)=8231 Pa`