Porosity Practice Problem 1
© 2007 Donald G. McGahan (aka soilman) All Rights Reserved
A soil sample has a total volume of 200 cm3 and the volume of water is 80 cm3 what is the volumetric water content?
Solution
Let VW equal the volume of water: VW = 80 cm3
Let VT equal the volume total (VA + VW + VS ): VT = 200 cm–3
Let θV represent the volumetric water content
Since θV = VW / VT
Then θV = 80 cm3 / 200 cm3 (or 80 cm3 200 cm–3)
Therefore θV = 0.40
Three things to note. First, while it is not necessary to place a zero prior to the decimal, since it is a non-zero number to the right of the decimal, it still looks better and is easer to read with the zero. Second, the solution is unit-less and is proofed as such because units were represented throughout the equations solution. Third, the question and solution stands independent since all the variables are defined, and the equation to derive the solution clearly stated.
Note: Use the unit conversions you know. Remember significant digits and rounding rules. Keep up with populating units throughout the calculations. Don’t skip calculation steps not matter how simple. In a time crunch, when you are tired, and perhaps stressed being able to step through even the simplest conversion or calculation as a recheck is invaluable.