Subsubsection Unit Conversions
Frequently, engineers need to find length equivalents between different systems of measurement. For example, in the construction of a ship there may be different contractors, some of whom use US standard measurement and others who use metric. Since the agreed upon system is metric, conversions are required to standardize all measurements.
Conversion of units is the process to convert between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects. Unit conversion is often easier within the metric or the SI than in others, due to the regular 10-base in all units and the prefixes that increase or decrease by 3 powers of 10 at a time.
The unit-factor method or the unity bracket method is a widely used technique for unit conversions using the rules of algebra.
Thefactor-label method is the sequential application of conversion factors expressed as fractions and arranged so that any dimensional unit appearing in both the numerator and denominator of any of the fractions can be cancelled out until only the desired set of dimensional units is obtained. For example, 10 miles per hour (mi/hr or mph) can be converted to meters per second (m/s) by using a sequence of conversion factors as shown below:
