7.1 Basic Terms and Conversions Within the Metric System 411 Recall from your science courses that most of the measurements were in metric units. For example, in chemistry you may have worked with liter containers, and in physics you may have worked with a mass in kilograms rather than a weight in pounds. Have you ever asked yourself why the sciences use metric measurement? In this section, we will explain some benefits of using the metric system. Basic Terms and Conversions Within the Metric System SECTION 7.1 LEARNING GOAL Upon completion of this section, you will be able to: 7 Perform conversions within the metric system. Why This Is Important In addition to being used in science courses, most countries use the metric system for measurement. A knowledge of the metric system will help you not only at home but also when you travel to other countries. It will also help you when you shop for electronic and other products. Most countries of the world use the Système international d’unités or SI system . The SI system is generally referred to as the metric system in the United States. The metric system was named for the Greek word metron, meaning “measure.” The metric system was first developed in France during the French Revolution. Two systems of weights and measures exist side by side in the United States today: the U.S. customary system and the metric system. In this chapter, we will discuss the metric measurements of length, area, volume, mass, and temperature. Using the metric system has many advantages. Some of them are summarized here. 1. The metric system is the worldwide accepted standard measurement system. All industrial nations that trade internationally, except the United States, use the metric system as the official system of measurement. 2. In the metric system there is only one basic unit of measurement for each physical quantity. In the U.S. customary system, many units are often used to represent the same physical quantity. For example, when discussing length, inches, feet, yards, miles, and so on are used. Converting from one of these units to the other is often a tedious task. In the metric system, many conversions can be made by simply moving the decimal point. 3. The SI system is based on the number 10, and there is less need for fractions because most quantities can be expressed as decimals. m A meter (bottom figure) is a little longer than a yard (top figure). Did You Know? Lost in Space m The missing Mars Climate Orbiter In September 1999, the United States lost a $125 million spacecraft, the Mars Climate Orbiter , as it approached Mars. Two spacecraft teams, one at NASA’s Jet Propulsion Laboratory (JPL) and the other at a Lockheed Martin facility, were unknowingly exchanging some vital information in different measurement units. The spacecraft team at Lockheed sent some measurements to the spacecraft team at JPL using U.S. customary units. The JPL team assumed the information it received was in metric units. The mix-up in units led to the JPL scientists giving the spacecraft’s computer the wrong information, which led to the spacecraft entering the Martian atmosphere, where it burned up. NASA has taken steps to prevent this error from ever happening again. National Aeronautics and Space Administration Klaus Vedfelt/Digital Vision/Getty Images Siede Preis/Photodisc/ Getty Images
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