Page 387 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

Conversion of American and British volume units into Work, Energy, Heat, Power
SI units: Work equals force times distance, N · m = J
1 fluid ounce (USA) = 29.57 mL (joule), or pressure times volume, (N · m ) · m 3
–2
1 fluid ounce (UK) = 28.47 mL
1 liquid gallon (USA) = 3.785 L = J. Energy and heat are also expressed in J.
1 liquid gallon (UK) = 4.546 L Other units of work, heat, and energy are
1 pint (USA) = 473.12 mL converted into J as follows:
-7
1 pint (UK) = 569.4 mL 1 erg = 10 J = 0.1 µJ
1 cal ! 4.185 J
Velocity, Frequency, Acceleration 1 kcal ! 4185 J = 4.185 kJ
Velocity is the distance traveled per unit time 1 Ws = 1 J
6
–1
(m · s ). This is an expression of linear velocity, 1 kWh = 3.6 · 10 J = 3.6 MJ.
whereas “volume velocity” is used to express Power equals work per unit time and is ex-
–1
the volume flow per unit time. The latter is ex- pressed in watts (W), where W = J · s . Heat
3
–1
pressed as L · s –1 or m · s . flow is also expressed in W. Other units of
Frequency is used to describe how often a power are converted into W as follows:
–7
periodic event (pulse, breathing, etc.) occurs 1 erg · s –1 = 10 W = 0.1 µW
per unit time. The SI unit of frequency is s –1 or 1 cal · h –1 = 1.163 · 10 W = 1.163 mW
-3
hertz (Hz). min
1 metric horse power (hp) = 735.5 W =
is also commonly used:
–1
Appendix min –1 = 1/60 Hz ! 0.0167 Hz. –2 0.7355 kW.
Acceleration, or velocity change per unit
–1
–1
deceleration is equivalent to negative accelera-
The base unit of mass is the kilogram (kg),
13 time, is expressed in m · s · s = m · s . Since Mass, Amount of Substance
tion, acceleration and deceleration can both be which is unusual insofar as the base unit bears
–2
expressed in m · s . the prefix “kilo”. Moreover, 1000 kg is defined
as a metric ton* instead of as a megagram.
Force and Pressure Weight is the product of mass and gravity (see
Force equals mass times acceleration. Weight above), but weight scales are usually cali-
is a special case of force as weight equals mass brated in units of mass (g, kg).
times acceleration of gravity. Since the unit of
mass is kg and that of acceleration m · s , force British and American units of mass are converted into
–2
SI units as follows.
is expressed in m · kg · s –2 = newton (N). The Avoirdupois weight:
older units of force are converted into N as fol- 1 ounce (oz.) = 28.35 g
lows: 1 pound (lb.) = 453.6 g
1 dyn = 10 N = 10µN Apothecary’s and troy weight:
-5
-3
1 pond = 9.8 · 10 N = 9.8 mN. 1 ounce = 31.1 g
Pressure equals force per unit area, so the SI 1 pound = 373.2 g.
unit of pressure is N · m –2 = pascal (Pa). The mass of a molecule or an atom (molecular
However, the pressure of bodily fluids is usu- or atomic mass) is often expressed in daltons
ally measured in mm Hg. This unit and other (Da)*. 1 Da = 1/12 the mass of a C atom, equi-
12
units are converted into SI units as follows: valent to 1 kg/Avogadro’s constant = 1 kg/
1 mm H 2O ! 9.8 Pa (6.022 · 10 ):
23
1 cm H 2O ! 98 Pa 1 Da = 1.66 · 10 -27 kg
1 mm Hg = 133.3 Pa = 0.1333 kPa 1000 Da = 1 kDa.
1 torr = 133.3 Pa = 0.1333 kPa
1 technical atmosphere (at) ! 98.067 kPa
1 physical atmosphere (atm) = 101.324 kPa
1 dyne · cm –2 = 0.1 Pa
1 bar = 100 kPa.
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Despopoulos, Color Atlas of Physiology © 2003 Thieme
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