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Measurements We know that an object moving through the air creates certain forces. We are most interested in aerodynamic forces sufficient to allow flight. Both the object and the forces created must be measured. We can measure mass, time, length, and temperature. Units Units are used to define measurements so that everyone knows exactly how much. Some examples of units are meter, foot, inch, centimeter or a mile. If a planner draws a bridge and says it is 1000 long and the builder looks at the plans and says it is one short, this is a problem! Are they talking about a meter, a foot or an inch? So, units are very important! A measurement should always include 2 things: a number and a unit. Some examples everyone may know include things like: there are 20 minutes until recess; it takes 10 days to drive across the country; a desk top is 20 inches wide and 25 inches long; a recipe uses 2 cups of flour; it is 85 degrees outside today. Each of these measurements includes a number and a unit. Mass Everything, whether it is a solid, liquid, or a gas has mass. It is a measure of how much of the substance is there - how many molecules. Sometimes mass is expressed as weight, even though they are not the same. In the metric system, the units for mass are grams, kilograms (1000 grams) or milligrams (1/1000 grams). In the American unit (called the English system), the weight of the substance is used, in pounds or ounces. A pound is 16 ounces. Often abbreviations are used for the units: a gram is g, a kilogram is kg, a milligram is mg, a pound is lb. and an ounce is oz. Time The easiest way to think of time is how long it takes something to happen. It may take 10 minutes to drive to school; it may take an hour to eat dinner. The units for time are the same around the world: seconds, hours, days, years. In aerodynamics, a common time measurement is how long it takes an object to go from one point to another or from point A to point B. Length How long is it? How far is it? These are questions heard every day. Length is a quality used by many people to define an object. A pencil is 7 inches long. A student is 4 feet tall. A swimming pool is 2 meters deep. The most common units for the metric system are a centimeter, a meter (100 centimeters) and a kilometer (1000 meters). In the English system, that most Americans use, common units are the inch, a foot (12 inches), or a mile (5280 feet). These units may be abbreviated: centimeter as cm, meter as m, kilometer as km, inch as in, foot or feet as ft, and a mile as mi. In addition to the length of an object, it is often useful to know the area or volume of the object in question. The area is how much room is on a surface like the floor of the classroom or the surface of a wing. Area is found by multiplying one length by another length. The result is called "square units". For example, if a room was 20 feet by 25 feet long you would multiply 20 X 25 = 500 square feet. Many common measurements in science and engineering include square feet or square meters. Another common measurement is an acre, 40,000 square feet. The volume of an object can either be how much space is available inside an object, like a fuel tank or how much actual material is inside a specific place. Volume has three measurements, length, height and width (all of these can be called lengths). Multiplying these together equal volume. The result is cubed. For example, a 12 inch long section of a 2 by 4 board (2 X 4 X 12 inches) would have a volume of 96 cubic inches. Cubic feet, cubic meters, gallons, liters, and cubic centimeters (cc for short) are all common units for volume. Temperature
The quality of temperature is a measure of how hot or cold something
is. A thermometer is commonly used to determine the temperature of an
object. Everything has a tempertature - the rocks, trees, people, air.
The weather report in the newspaper usually gives the high and low
temperatures of the air each day. The common units for temperature are
degrees Fahrenheit or degrees Celsius (what used to be Centigrade). In
America, almost everyone uses the Fahrenheit scale. In science and
engineering, however, temperatures can be reported using either
scale. The way this is shown is either 85° F or
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