Physical constants
Empirically determined values
G = 6.674 2×10í^11 N·m^2 /kg^21.5 - Length
If you live in a country that uses the metric system, you already have an intuitive sense
of how long a meter is. You are likely taller than one meter, and probably shorter than
two. If you are a basketball fan, you know that male professional basketball centers
tend to be taller than two meters while female professional centers average about two
meters.
If you live in a country, such as the United States, that still uses the British system, you
may not be as familiar with the meter. A meter equals about 3.28 feet, or 39.4 inches,
which is to say a meter is slightly longer than a yard. The kilometer is another unit of
length commonly used in metric countries. You may have noticed that cars often have
speedometers that show both miles per hour and kilometers per hour. A kilometer
(1000 meters) equals about 0.621 miles. In track events, a metric mile is
1.50 kilometers, which is about 93% of a British mile.
Centimeters (one one-hundredth of a meter) are also frequently used metric units. One
inch equals 2.54 centimeters, so a centimeter is about four tenths of an inch. One foot
equals 30.48 centimeters. You see some common abbreviations in Equation 1 to the
right: “m” for meters, “km” for kilometers and “cm” for centimeters.Length
Measured in meters (m)
Distance light travels in
3.335 640 95×10í^9 seconds1 meter (m) = 3.28 feet
1 kilometer (km) = 0.621 miles
1 centimeter (cm) = 0.394 inches(^10) Copyright 2000-2007 Kinetic Books Co. Chapter 01