--- loncom/html/adm/help/tex/Physical_Units.tex	2003/01/24 22:32:08	1.1
+++ loncom/html/adm/help/tex/Physical_Units.tex	2008/03/06 01:54:18	1.6
@@ -2,6 +2,23 @@
 \section*{Physical Units Accepted by LON-CAPA}
 The following subsections show the physical units that LON-CAPA accepts. 
 The symbols must be used when entering the units, for example {}``35 kg''.
+
+Note that compound units are formed by using *, / and ^. For example, an acceleration might
+be in terms of ``m/s^2'' or meters per second squared. This could also be expressed as``m/s/s''.
+Units of Newton-meters (for torque) would be entered as ``N*m''. Parentheses may be used to guarantee
+the correct sense of the unit. Kilometers per Ampere-hour could be written as ``km/(A*hr)'' or
+``km/A/hr'' but not ``km/A*hr''. The last option would be interpreted as kilometer times hours per Ampere.
+
+LON-CAPA will automatically perform some conversions between units of the same dimension
+when units are provided for a problem.
+You can provide an answer of ``1.45 km'' for a distance.
+ If the computer expects the answer in cm, it will convert your answer before comparing
+against the numerical solution.
+
+Please note that if your units are inappropriate, the computer has no way of checking
+the appropriateness of your answer.  If units are required, only once appropriate
+units are provided will the system check your numerical answer.
+
 \subsection*{Base Units}
 \begin{verbatim}
 # name      symbol     comment
@@ -13,6 +30,7 @@ ampere          A      # electric curren
 kelvin          K      # thermodynamic temperature
 mole            mol    # amount of substance
 candela         cd     # luminous intensity
+decibel         dB     # log of pressure amplitude
 \end{verbatim}
 \subsection*{Prefixes}
 \begin{verbatim}
@@ -27,6 +45,7 @@ giga             G         10^9
 mega             M         10^6
 kilo             k         10^3
 hecto            h         10^2
+deca             D         10^1
 
 deci             d         10^-1
 centi            c         10^-2
@@ -45,9 +64,11 @@ yocto            y         10^{-24}
 # name       symbol    comment
 
 gram            g      # mass
-hour            hr     # time
 minute          min    # time
+hour            hr     # time
+hour            h      # time
 day             day    # time
+day             days   # time
 year            yr     # time
 pound           lb     # mass
 ounce           oz     # mass
@@ -79,6 +100,10 @@ ohm             ohm    # electric resist
 ohm             ohms   # electric resistance
 ohm             Ohm    # electric resistance
 ohm             Ohms   # electric resistance
+mho             mho    # electric conductance
+mho             mhos   # electric conductance
+mho             Mho    # electric conductance
+mho             Mhos   # electric conductance
 siemens         S      # electric conductance
 farad           F      # electric capacitance
 tesla           T      # magnetic flux density
@@ -90,9 +115,23 @@ steradian       sr     # solid angle
 lumen           lm     # luminous flux
 lux             lx     # illuminance
 becquerel       Bq     # activity (radioactive)
+curie           Ci     # activity (radioactive)
 gray            Gy     # absorbed dose (of radiation)
 sievert         Sv     # dose equivalent (dose equivalent index)
 astroUnit       AU     # mean distance earth to sun
+celcius         degC   # multiplicatively OK
+farenheight     degF   # multiplicatively OK
+molarity        M      # chemisty
+amu             amu    # atomic mass unit
+amu             u      # atomic mass unit
+lightspeed      c      # speed of light
+cubiccentimeter cc     # cubic centimeter
+electroncharge  e      # elementary charge
+hbar            hbar   # Planck constant
+milesperhour    mph    # miles per hour
+rpm             rpm    # rounds per minute
+rpm             rpms   # rounds per minute
+parsec          pc     # parsec
 \end{verbatim}
 \subsection*{Interpretation}
 The coded units are interpreted in the order of basic unit,