2. Pressure
P = Force / area
Pressure in a liquid
Pressure in a liquid = weight of liquid
area occupied by liquid
Vol = area x height occupied by the liquid in the
container = hA
Mass = density x vol = ρhA
Weight = mg
Pressure = W/A = mg/A
Substitute for mass => P = ρhAg/A = ρhg
P = W/A = ρhg
3. Transmission of pressure in fluids
PASCAL’S PRINCIPLE: The pressure applied
to an enclosed fluid is transmitted
undiminished to every portion of the fluid
and the walls of the containing vessel.
Application: Hydraulic press: car brakes
4. Atmospheric pressure
Pressure exerted by column of air up to
80km high
It is essentially due to the weight of air above
the earth surface and decreases with lenght
(altitude)
Atmospheric pressure =hρg
ρ is density of medium
5. Measurement of pressure
Simple barometer: Used to measure
atmospheric pressure
fortin barometer: for more accurate
mesurement
Aneroid barometer: a compact barometer that
does not work with liquid or mercury
