A unit conversion expresses the same property as a different unit of measurement. For instance, time can be expressed in minutes instead of hours, while distance can be converted from miles to kilometers, or feet, or any other measure of length.
Often measurements are given in one set of units, such as feet, but are needed in different units, such as chains. A conversion factor is a numeric expression that enables feet to be changed to chains as an equal exchange. A conversion factor is a number used to change one set of units to another, by multiplying or dividing. When a conversion is necessary, the appropriate conversion factor to an equal value must be used.
For example, to convert inches to feet, the appropriate conversion value is 12 inches equal 1 foot. To convert minutes to hours, the appropriate conversion value is 60 minutes equal 1 hour.
The table is set up so all the units cancel except for the unit desired. First, convert the given unit ms to the base unit—in this case, seconds—and then convert seconds to the final unit, megaseconds:. A pharmacist dispenses drugs that have been prescribed by a doctor. Although that may sound straightforward, pharmacists in the United States must hold a doctorate in pharmacy and be licensed by the state in which they work.
Most pharmacy programs require four years of education in a specialty pharmacy school. Pharmacists must know a lot of chemistry and biology so they can understand the effects that drugs which are chemicals, after all have on the body. Pharmacists can advise physicians on the selection, dosage, interactions, and side effects of drugs. They can also advise patients on the proper use of their medications, including when and how to take specific drugs properly.
Pharmacists can be found in drugstores, hospitals, and other medical facilities. Curiously, an outdated name for pharmacist is chemist , which was used when pharmacists formerly did a lot of drug preparation, or compounding. Learning Objectives Convert a value reported in one unit to a corresponding value in a different unit. Any fraction that has the same quantity in the numerator and the denominator has a value of 1: We know that cm is 1 m, so we have the same quantity on the top and the bottom of our fraction, although it is expressed in different units.
This is how you construct a conversion factor to convert from one unit to another. Significant Figures in Conversions How do conversion factors affect the determination of significant figures?
What is this volume in milliliters? A hummingbird can flap its wings once in 18 ms. How many seconds are in 18 ms? Solution We start with what we are given, 4. We want to change the unit from liters to milliliters. There are 1, mL in 1 L.
Conversion Factors From Different Units Conversion factors can also be constructed for converting between different kinds of units. We can write that relationship as follows: Density can be used as a conversion factor between mass and volume. Solution Because we are starting with grams, we want to use the conversion factor that has grams in the denominator. Looking Closer: Density and the Body The densities of many components and products of the body have a bearing on our health.
Problem Solving With Multiple Conversions Sometimes you will have to perform more than one conversion to obtain the desired unit. Neither conversion factor affects the number of significant figures in the final answer.
Career Focus: Pharmacist A pharmacist dispenses drugs that have been prescribed by a doctor. Key Takeaway A unit can be converted to another unit of the same type with a conversion factor.
The 3. Because m, the abbreviation for meters, occurs in both the numerator and the denominator of our expression, they cancel out:. In the final answer, we omit the 1 in the denominator. Thus, by a more formal procedure, we find that 3.
A generalized description of this process is as follows:. You may be wondering why we use a seemingly complicated procedure for a straightforward conversion. In later studies, the conversion problems you encounter will not always be so simple.
If you master the technique of applying conversion factors, you will be able to solve a large variety of problems. Yes, it does; it has the same quantity in the numerator as in the denominator except that they are expressed in different units. Why did we not use that conversion factor?
If we had used the second conversion factor, the original unit would not have canceled, and the result would have been meaningless. Here is what we would have gotten:. For the answer to be meaningful, we have to construct the conversion factor in a form that causes the original unit to cancel out.
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Learning Objectives To convert a value reported in one unit to a corresponding value in a different unit using conversion factors. Converting Between Units with Conversion Factors A conversion factor is a factor used to convert one unit of measurement into another.
Conversions in the metric system, as covered earlier in this chapter. Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. Conversion Factor Definition and Examples. Measuring and Understanding Wood Volumes. Math Glossary: Mathematics Terms and Definitions. International System of Measurement SI. Enthalpy Definition in Chemistry and Physics. Calculating the Concentration of a Chemical Solution.
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