Lal R., Shukla M.K. Principles of Soil Physics
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Appendix B
Mathematical Signs and Symbols
α is proportional to
= is equal to
≈ is approximately equal to
≠ is not equal to
> is greater than
is much greater than
< is less than
is much less than
≤ is less than or equal to
≥ is greater than or equal to
Σ sum of
average value of x
∆x change in x
∆x→0 ∆x approaches zero
n! n(n−1)(n−2)
Appendix C
Prefixes for SI Units
Factor Prefix Abbreviation
10
−1
deci d
10
−2
centi c
10
−3
milli m
10
−6
micro M
10
−9
nano n
10
−12
pico p
10
−15
femto f
10
−18
atto a
10 deca da
10
2
hecto h
10
3
kilo k
10
6
mega M
10
9
giga G
10
12
tera T
10
15
peta P
10
18
exa E
Appendix D
Values of Some Numbers
π=3.1415927
e=2.7182818
ln 2=0.6931472
ln 10=2.3025851
log
10
e=0.4342945
rad=57.2957795
Appendix E
SI Derived Units and Their Abbreviations
Quantity Unit Abbreviation In terms of base units
a
Force newton N kg m/s
2
Energy and work joule J kg m
2
/s
2
Power watt W kg m
2
/s
3
Pressure pascal Pa kg/ms
2
Frequency hertz Hz s
−1
Electric charge coulomb C As
Electric potential volt V kg m
2
/A s
3
Electric resistance ohm Ω kg m
2
/(A s
3
)
Capacitance farad F A
2
s
4
/(kg m
2
)
Magnetic field tesla T kg/(A s
2
)
Magnetic flux weber Wb kg m
2
/(a s
2
)
Inductance henry H kg m
2
/(s
2
A
2
)
a
kg=kilogram (mass), m=meter (length), s=second (time), A=ampere (electric current).
Appendix F
Unit Conversion Factors
Appendix F 619
Appendix G
Unit Conversions (Equivalents)
LENGTH
1 in=2.54 cm
1 cm=0.394 m
ft=30.5 cm
m=39.37 in=3.28 ft
mi=5280 ft=1.61 km
km=0.621 mi
nautical mile (U.S.)=1.15 mi=6076 ft=1.852 km
fermi=1 femtometer (fm)=10
−15
m
angstrom (A)=10
−15
m
1 light-year=9.46×1015 m
1 par sec=3.26 light years
TIME
1 day=8.64×104 s
1 year=3.156×107 s
SPEED
1 mi/h=1.47 ft/s=1.609 km/h=0.447 m/s
1 km/h=0.278 m/s=0.621 mi/h
1 ft/s=0.305 m/s=0.682 mi/h
1 m/s=3.28 ft/s=3.60 km/h
1 knot=1.151 mi/h=0.5144 m/s
ANGLE
1 radian (rad)= 7.30 =57°18′
1=0.01745 rad
1 rev/min (rpm)=0.1047°rad/s
MASS
1 atomic mass unit (u)=1.6605×10
−27
kg
1 kg=14.6 kg
1 kg=0.0685 slug
(1 kg has a weight of 2.20 lb where g=9.81 m/s
2
)
FORCE
1 lb=4.45 N
1 N=10
5
dyne=0.225 lb
ENERGY AND WORK
1 J=10
7
ergs=0.738 ft.lb
1 ft. lb=1.36 J=1.29×10
−3
Btu=3.24×10
−4
kcal
1 kcal=4.18×10
3
J=3.97 Btu
1 Btu=2.52 cal=278 ft 1b=1054J
1 eV-1.602×10
−19
J
1 kWh=3.60×10
6
J=860 kcal
POWER
1 W=1 J/s=0.738 ft.lb/s=3.42 Btu/h
1 hp=550 ft.lb/s=746 W
PRESSURE
1 atm=1.013 bar=1.013×10
5
N/m
2
=14.7 lb/in.2=760 torr
1 lb/in.
2
=6.90×10
3
N/m
2
1 Pa=1 N/m
2
=1.45×10
−4
lb/in.
2
Appendix G 621
Appendix H
Conversion Factors for Non-SI Units
Unit Abbreviation Value
atmosphere atm 101325 Pa (definition)
torr torr 133.322 Pa=1/760 atm
atomic mass unit amu 1.66054×10
−27
kg
bar bar 1×10
5
Pa
electron volt eV 1.602178×10
−19
J
poise P 0.1 kgm
−s
liter L 1×10
−3
m
3
=1dm
3
angstrom A 1×10
−10
m
debye D 3.335641×10
−30
Cm
calorie cal 4.184 J (definition)
inch in 0.0254 m (definition)
pound lb 0.4536 kg
Appendix I
Conversion Among Units of Soil Water
Potential
1 atmosphere =1.013×105 Nm
−2
=1.013×105 Pa=101.3 kPa
=1.013 bar
=1.013×10
6
dynes cm
−2
=14.7 PSI or 2.12×103 lbft
−2
=76 cm of Hg or 760 mm of Hg or 760 torr 1.03×10
4
mm-H
2
O at 4°C
1 bar =105 Nm
−2
1 dyne cm
−2
=0.1 N m
−2
1 Kg cm
−2
=9.85×104 Nm
−2
1 PSI (lb m
−2
) =6.90×10
3
Nm
−2
1 lb m
−2
=47.9 Nm
−2
1 lb ft
−2
=47.9 Nm
−2
1 cm-Hg =1.33×103 Nm
−2
1 mm-Hg =133 N m
−2
=1 torr
1 mm H
2
O at 4°C =9.81 Nm
−2