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8°F, or 1°F = 100/180°C = 5/9°C = 5/9 K. Note that these formulas apply only to temperature differences or changes. They do not take into account the differing zero points of the three temperature scales. In order to convert a temperature measurement from one scale to another, we must have formulas that allow for both the differing unit sizes and the differing zero points. The following is one logical approach that can be taken to derive a formula for converting Fahrenheit measurements to Celsius measurements.

These are equivalent operations and you should feel comfortable with either method. In each case, "cents" and "doz" cancel out, leaving only "apples," as we had hoped. A somewhat more sophisticated method for setting up the problem is to use the negative exponent, - 1, for units that appear in the denominator of a set of units. Thus the term "per dozen" may be written as doz"1. 5 mi (one mile is 5280 ft). 30 Use of Dimensions SOLUTION: To find the number of feet, we need the product shown in the equation ft feet = 1 5 nrt x 5280 — vert = 7920 ft Alternatively, we may use the solution feet = 1 5 jot x 5280 ft mi'1 = 7920 ft PROBLEM: Find the number of gallons in 5 cu yd (also written as yd3), using the conversion factors 231 in3 = 1 gal 3 ft = 1 yd 12 in = 1 ft SOLUTION: 3 1 gal gallons = 5 yd 3 x (3 -7) x (12 l-^- x —-—3 231 in \ yd/ \ it, * 231;** = 1010 gal PROBLEM: Find a conversion factor F by which you can convert yd 3 to gallons SOLUTION: A conversion factor can be developed from other known factors by calculating a value of F that will satisfy the equation gal = (yd)3[F] F must have such units that, when they are substituted in this equation, they will cancel yd 3 and yield only gal as the net result, as follows = 202 Problems A 31 Thus, if you want to convert 20 yd3 to gallons, you merely multiply 20 by 202, as follows: gal = (20 >d*) (202 |p\ = 4040 gal PROBLEM: If a runner does the 100 yd dash in 10 seconds, what is his speed in miles per hour?

Assume a plane (not curved) meniscus. 40 Units of Scientific Measurements 24. 010 mm thick. How thick will the film be if the bubble is expanded to 15 inches in diameter? 25. 00 cm on an edge. What is the surface area? 00 mm on an edge. What is the surface area after crushing? (c) Further crushing gives cubes measuring 100 A on an edge. What is the surface area now? How many football fields (160 ft x 100 yd) would this make? 26. The unit of viscosity (77) is called a poise. Viscosity is determined experimentally by measuring the length of time (t) for a certain volume (V) of liquid to run through a capillary tube of radius R and length L under a pressure P , according to the Poiseuille equation P-rrtR4 What are the units of a poise in the centimeter-gram-second (cgs) system?