Summary

 

Fbouyant = wliquid

Several different systems of units are in common useage when dealing with pressure:

1 pascal = 1 Pa = 1 [ N / m2 ]

1 atm = 1.013 x 105 Pa

1 bar = 100 kPa = 1 x 10 5 Pa

1 atm = 1.013 bar

1 atm = 101.3 kPa

1 mm Hg = 133 Pa

1 atm = 760 mm Hg

1 Torr = 1 mm Hg

1 atm = 760 Torr

(Units of pounds per square inch (PSI) are also commonly used but we will avoid those in this course).

1 A 1 v1 = 2 A 2 v2

For many situations -- for most situations involving a liquid but not a gas -- we can assume the density does not change. This is called an incompressible fluid. For those cases,

A 1 v1 = A 2 v2

(1/2) v2 + P + g y = constant

or

(1/2) 1 v12 + P1 + 1 g y1 = (1/2) 2 v22 + P2 + 2 g y2

If the vertical height y does not change, this means

(1/2) v2 + P = constant

or

(1/2) 1 v12 + P1 = (1/2) 2 v22 + P2
Bouyancy

Homework
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(c) 2005, Doug Davis; all rights reserved