# Formulas and Important Values ```Municipal 1 – Formulas and Important Values
Newtons second
law of motion
Standard Density
Relative Density
(Specific Gravity)
Density
For water at 20 &deg;
capillary rise h
Bulk Modulus of
Elasticity
Pressure
Pressure in a fluid
pgh
Standard
Atmospheric
pressure
Gauge Pressure
Absolute Pressure
Relation of absolute
and gauge pressures
Density of Alcohol
Manometer
Pressure in
diagrams
Pressure Differential
To maintain
equilibrium
Density of Mercury
F=m*a
F=m*9.81
1000 kg/m^3
Density
-----------------Standard Density (1000 kg/m^3)
Specific Gravity(given) x Standard Density (1000)
h= 30/Diameter of tube
For water in glass tubes with D over 12mm, capillary rise is negligible
𝐷𝑝 (𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒)
𝐸=
𝐷𝑣(𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑜𝑙𝑢𝑚𝑒)
𝑣 (𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒)
𝑃𝑡𝑜𝑡𝑎𝑙 = 𝑃𝑠𝑢𝑟𝑓𝑎𝑐𝑒 + 𝑝𝑔ℎ
(density) * (acceleration of gravity) * (depth of the fluid)
“ρ (roe)” x 9.81x height in meters
kPa is meters, Pa is mm ex.
If asked 570 kPa in mm change to… 570,000 Pa for height in mm
101.325 kPa, 760mm of mercury or 10.34m of water
Measured using local atmospheric or barometric pressure as the
datum
Measured by using absolute 0 pressure as the datum
𝑃𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 = 𝑃𝑎𝑡𝑚𝑜𝑠𝑝ℎ𝑒𝑟𝑖𝑐 + 𝑃𝑔𝑎𝑢𝑔𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒
Use this to convert gauge pressure to absolute pressure
You can obtain negative pressure; it just means that it lies between
atmospheric and absolute pressure
Specific measure of liquid pressure above a vertical datum:
ℎ𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 = ℎ𝑎𝑡𝑚𝑜𝑠𝑝ℎ𝑒𝑟𝑖𝑐 + ℎ𝑔𝑎𝑢𝑔𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒
0.79
Helps us find pressure within pipes
Pressure going down is negative
Pressure going up is positive
To find pressure at a certain point start at the other end and add
up all the pressures
𝑃𝐵 − 𝑃𝐴
P1 = P2
13.6
Municipal 1 – Formulas and Important Values
```