# Homework Help: Fluid Mechanics: Differential Hg Manometer

1. Sep 21, 2009

### nicmat42

1. The problem statement, all variables and given/known data
A differential mercury manometer is connected to pipe A containing gasoline (SG=0.65), and to pipe B containing water. Determine the differential reading, h, corresponding to a pressure in A of 20kPa and a vacuum of 150 mm Hg in B.

2. Relevant equations
Distance from pipe A to fill line is 0.3 m and distance from pipe B to other fill line is 03 m.

3. The attempt at a solution
I have done a few manometer problems before, however, I am not sure what to make of the "vacuum of 150 mm Hg in B". I do not know what this is implying to the problem?
If someone could kindly explain I would be very grateful and will be able to complete the question.
Thanks

2. Sep 22, 2009

### Redbelly98

Staff Emeritus
It sounds like they are talking about the pressure relative to 1 atm (760 mm Hg).

So the "vacuum of 150 mm Hg" means an absolute pressure of (760-150) or 610 mm Hg.

This probably means the 20 kPa pressure is really 1 atm + 20 kPa.