VARIATION OF PRESSURE WITH DEPTH
UNIT PRESSURE or PRESSURE, P
Pressure is the force per unit area exerted by a liquid or gas on a body or a surface,
with the force acting at right angles to the surface uniformly in al
...
VARIATION OF PRESSURE WITH DEPTH
UNIT PRESSURE or PRESSURE, P
Pressure is the force per unit area exerted by a liquid or gas on a body or a surface,
with the force acting at right angles to the surface uniformly in all directions.
The SI unit used for pressure is Pascal, Pa equal to N/m2.
PASCAL’S LAW
Pascal’s Law, introduced by French Mathematician Blaise Pascal, states that “Any two
points at the same elevation in a continuous mass of the same static fluid will be at the
same pressure.”
o GAGE PRESSURE (RELATIVE PRESSURE), Pgage
Gage pressures are above or below the atmosphere and can be measured by
pressure gages or manometers.
o ATMOSPHERIC PRESSURE, Patm
Atmospheric pressure is the pressure at any one point on earth’s surface from
the weight of the air above it.
Under normal conditions at sea level:
1 atm = 2166 lb/ft
= 14.7 psi
= 29.9 in. Hg
= 760 mm Hg
= 101.325 KPa
o ABSOLUTE PRESSURE, Pabs
The intensity of pressure above absolute zero is called absolute pressure.
Obviously, a negative absolute pressure is impossible.
Pabs = Pgage + Patm
Note: Unless otherwise specified in the problem, the term pressure signifies gage pressure.
VARIATION OF PRESSURE WITH DEPTH IN A FLUID
The difference in pressure between any two points in a homogeneous fluid at
rest is equal to the product of the unit weight of the liquid and the vertical distance
between the points.
The pressure at any point below the free surface of
a liquid equals the product of the unit weight of the
liquid and the depth of the point.
[Show More]