If you express a measured quantity in two different metric units, then the two measurements are metric equivalents.A base unit is one that cannot be expressed in terms of other units.The prefixes in the metric system are multiples of 10.The metric system uses a number of prefixes along with the base units.The metric system is an international decimal-based system of measurement.Common metric equivalents are shown below. If you express a measured quantity in two different metric units, then the two measurements are metric equivalents. You can express a given measurement in more than one unit. Common Prefixes in the International System PrefixĬommon metric units, symbols, and relationships to a base unit are shown below. When milli- is placed in front of meter, as in millimeter, the measure is now of a meter. When the prefix centi- is placed in front of gram, as in centigram, the measure is now of a gram. ![]() Each base unit can be combined with different prefixes to define smaller and larger quantities. The base unit of mass is the gram (g), that of length is the meter (m), and that of volume is the liter (L). A base unit is one that cannot be expressed in terms of other units. The metric system uses a number of prefixes along with the base units. This is true about all parts of the English system: you have to memorize all the facts that are needed for different measurements. What happens if you never memorized this fact? Of course you can look it up online or elsewhere, but the point is that this fact must be given to you, as there is no way for you to derive it out yourself. But now you need to know how many feet are in a mile. For instance, if you need to know how many inches are in a foot, you only need to remember what you at one time memorized. Let’s consider the English system – that is, the one that is in everyday use in the US as well as England – to explain why the metric system is so much easier to manipulate. Because the metric system is a decimal system, making conversions between different units of the metric system are always done with factors of ten. The metric system is an international decimal-based system of measurement. The requirements of science in the 1600s, 1700s, and 1800s necessitated even more accurate, reproducible measurements. Copies could be made of these objects and distributed so that everyone was using exactly the same units of measure. What was needed were objects that could be safely stored so they didn’t change over time. Of course, this standard would change when a new king was crowned. The length of the king’s foot could be marked on pieces of wood and everyone who needed to measure length could have a copy. To achieve more consistency, everyone could use the king’s foot as the standard. It should be apparent that measurements of a foot by two people could differ by a few inches. Because grains of wheat are fairly consistent in mass, the quantity of meat purchased could be balanced against some number of grains of wheat on a merchant’s balance. The grain is a unit of mass measurement that is based upon the mass of a single grain of wheat. The inch is based on the width of a man’s thumb, and the foot speaks for itself. Inch and foot are examples of measurement units that are based on parts of the human body. The names of several measurement units reflect these early efforts. Mankind’s first elementary efforts in measurement required convenient objects to be used as standards and the human body was certainly convenient. Land ownership required measurements of length and the sale of food and other commodities required measurements of mass.
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