W2, Part 2

Question 1

Pressure measurement

Answer 1

The force exerted per unit area.
GAGE- measured relative to atmospheric pressure, 0 is atmospheric pressure.
ABSOLUTE- measured relative to a perfect vacuum, 0 is the absence of pressure.
Absolute p= gage p+ atmospheric p.

Question 2

Atmospheric pressure and barometers

Answer 2

Patm= γh+ Pvap ( hydrostatic pressure* vapour pressure).
Patm.- the force exerted by the weight of the atmosphere on a unit of the earth’s surface.
Measured using a barometer (consists of a glass tube filled with mercury, height of mercury column= atmospheric pressure)
Equilibrium: height of mercury rises up until weight of mercury column= force exerted by atmosphere.
(Mars has a lower atmospheric pressure than earth, composed of CO2).

Question 3

How is specific weight defined

Answer 3

γ = ρ * g . Measure of how heavy a substance is for its size.

Question 4

How is specific gravity defined

Answer 4

S, density of a substance/ density of a reference substance.

Question 5

What is meant by γh

Answer 5

γ is the specific weight, density* gravity. H is the height of the fluid column.
So it is the pressure at the bottoms of a fluid column due to the weight of the fluid above.

Question 6

How to find the excess pressure

Answer 6

p= 2σ/ r,

Question 7

Define specific gravity

Answer 7

Density of a substance/ density of a reference substance.
Properties and characteristics of various substances.