Units  (Page 7/4)

Units

Introduction

Engineering is a field of study that involves a very high level of calculations. Thus students of engineering must become familiar with a wide range of formulas and computational methods. Virtually all the calculations that engineers perform involve the use of units. Because many calculations involve the use of multiple units, an engineer must become competent in the process of unit conversions. Unit conversions allow an engineer with the ability to convert units in one system of measurement (say, the British system of measure) to those of another system (say, the System Internationale or SI system of measure.)

Units and unit conversion are important not just to engineers, but all members of society. Everyday activities such as driving an automobile, shopping at a grocery store, or visiting an pharmacy illustrate situations where an individual experiences units and unit conversions. Let us consider driving an automobile. A simple glance at a vehicle’s speedometer reveals that the speed of the vehicle can be expressed in the units miles/hour or kilometers/hour. Depending upon the country in which you reside, gasoline is sold in the units of gallons or liters. At the grocery store, the volume of a can of your favorite soda is often expressed in terms of ounces or milliliters. Likewise, the dosage of cough syrup that you obtain from your local pharmacy can be expressed in terms of the units ounces or milliliters. This list of examples from everyday life that involve units can be expanded without bound.

Whenever an engineer deals with a physical quantity, it is essential that units be included. Units are especially important to engineers for they provide the ability for engineers to express their thoughts precisely and to provide meaning to the numerical values that result from engineering calculations. Units provide a means for engineers to communicate results among other engineers as well as laymen.

Units are an integral part of what could be called the language of engineering. As a student of engineering, you should become accustomed to the inclusion of units with virtually all your answers to engineering problems. Failure to include units with your numerical results can lead to your having points deducted from your grades on assignments, laboratory exercises and examinations.

Metric mishaps

Failing to include the proper units with the results of engineering calculations can lead to unanticipated failures in engineering systems. Serious errors that result from the dual usage of metric and non-metric units are often grouped under the heading of metric mishaps . Some common examples of metric mishaps include the following:

• According to the National Transportation Safety Board, confusion surrounding the use of pounds and kilograms often results in aircraft being overloaded and unsuited for flight.
• The Institute for Safe Medication Practices has reported that confusion between the units grains and grams is a common reason for errors associated with the dosage of medication.