- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2150) Unit Title: MEASUREMENTS ___________________________________________________________________________ (CLF2152) Topic: READING MEASURING TOOLS Time Year(s) 2 hours 1 / 2 / 3 / 4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (C-1) - Measure objects correctly with a ruler, tape, or framing square. (C-4) - Differentiate between U.S. Customary and metric measurement units (in linear, area, and volumetric measurements). Special Material and Equipment: Twelve-inch ruler divided to the 16th of an inch which also contains a metric scale References: Cooper, E. L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Evaluation: Quiz by instructor. TOPIC PRESENTATION: READING MEASURING TOOLS A. Measuring Tools 1. Measuring tools include tapes, rules, squares, calipers, and other devices used to determine specific distances. 2. They are used to measure length, width, height, depth, thickness, spacing, and clearances. B. Fractions in Measurement 1. Definition a. The term "fraction" means a part or portion of a whole. b. It is nearly impossible to use any form of measurement without having a way to express fractional parts, for example, feet and inches. c. A fraction may be expressed in three different ways without altering its value: 1) As a common fraction (3/4) 2) As a decimal fraction (.75) 3) As a percent fraction (75%) 2. Common Fractions a. The common fraction is the type most often used in measurement, as the word "common" implies. b. It is made up of a numerator and a denominator. 1) The numerator and denominator are two numbers separated by a line that indicates division. a) The numerator is the upper number. b) The denominator is the lower number. Example: 3 = numerator 4 = denominator 2) In the above example, the 4, or denominator, indicates the number of equal parts into which the unit is divided; and the 3, or numerator, indicates the number of these parts being considered. 3. Lowest Terms a. Fractions are easiest to work with if they are expressed in their lowest terms. b. A common fraction is in its lowest term if its numerator and denominator are divided by the one largest number that will divide evenly into both. Example: 24 / 8 = 3 32 / 8 = 4 4. Addition and Subtraction of Common Fractions a. Only fractions with like denominators can be added or subtracted. c. If the denominators are different, they must be reduced to the lowest common denominator without changing the value of the fractions. 1) The result--the sum or difference of the numerators--is placed over the common denominator. 2) This resulting fraction is then reduced to lowest terms. C. The Inch as a Unit of Measurement 1. The inch is the traditional unit of measurement for wood- and metalworking in the United States. a. It must be divided into smaller units to be useful for most applications. b. Some fine rules or scales may have as many as 32 marks per inch. 1) Each mark is 1/32 of an inch apart. 2) One-sixteenth inch is more commonly used as the smallest unit on a rule. c. Lines of different lengths are used to show 1/2, 1/4, and 1/8 of an inch on many measuring devices such as rules and squares. 1) No even fractions can exist on the different lines of the rule or scale. 2) This simplifies reading a rule by reducing fractions to their lowest term. NOTE: THE DIAGRAM BELOW IS NOT DRAWN TO SCALE. ____________________________________________________________________ | | | | | | | | | | | | | | | | | | 1/16 | 3/16 | 5/16 | 7/16 | 9/16 | 11/16 | 13/16 | 15/16 | | 1/8 | 3/8 | 5/8 | 7/8 | | | | | | | 1/4 | 3/4 | | | | | | | | | | | 1/2 | | | | | | | | | | 1 inch |___________________________________________________________________ D. The Millimeter as a Unit of Measurement 1. The millimeter (mm) is slightly smaller than 1/16 of an inch. 2. It is a very convenient unit for linear measurement without using fractions. a. It has the advantage of being 1/1000 of a meter and 1/10 of a centimeter. 1) This means one meter plus 250 millimeters equal 1 1/4 meters. 2) It is more convenient to write this as a decimal than as a common fraction. a) Using the decimal, 1 1/4 meters reads 1.250 meters. b) Similarly, 1 1/2 meters reads 1.500, or simply 1.5 meters. b. On many metric rules, each centimeter division contains 10 marks to represent millimeters. 1) Centimeters can be changed to millimeters by multiplying by 10. 2) Simply adding a zero to the centimeter's value obtains the millimeter value. 3) To change meters to millimeters, multiply by 1000. NOTE: THE DIAGRAM BELOW IS NOT DRAWN TO SCALE. | | 1 cm 2 cm | | | | | | | 1 mm | | | | |__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|_ _________________________________________________________ ACTIVITY: 1. Use a combined metric and standard ruler to measure various objects in the room to the nearest 16th of an inch and to the millimeter. 2. Use a measuring tape to measure the circumference of round objects and then record the readings. 3. Add and subtract inch and millimeter readings. _________________________________________________________ 6/27/91 OLR/tf #%&C