Applied Science - Science and Math (4A) Post Lab
 OBJECTIVES: Measuring linear and curved surfaces. Estimating unknown quantities.  VOCABULARY: centimeter curve estimate inch linear predict MATERIALS: rulers tape measure string Students measure different surfaces.
 BACKGROUND: Students traditionally learn how to measure straight items, but most objects in the real world are curved.  Metrology is the science of measurement and is a fundamental tool in all aspects of science and everyday living.  Imagine a carpenter who doesn't know how to measure?  Lord Kelvin (England) once stated "when you can measure what you are speaking about and express it in numbers, you know what you are speaking about and you know something about it; but when you cannot measure it, when you cannot express it, your knowledge is of a meager and unsatisfactory kind". Measurement involves a comparison of an unknown to a known quantity.  These known quantities are actually set standards derived by international agreement.  There is no magic in a meter, a yard, a foot, or a kilometer.  These lengths were arbitrary to start with and are subject to change.  They were used as a way to keep track of distance.  For instance, from 1889-1960, a meter was the distance between 2 marks on a metal bar.  Now it pertains to a certain number of wave lengths in a particular spectrum line. Students should also be aware that measurement is not always accurate, and many scientists take a margin of error into consideration.  The purpose of this measurement exercise is to review how to measure straight and curved items.   Students will practice predicting or estimating what each length will be. This skill needs to be practiced since many times a ruler is not available. Many carpenters can accurately predict measurements without a ruler because they practice linear measuring skills over and over. PROCEDURE:  Use the worksheet to guide the activity.    Discuss how to measure curved surfaces by taking a string and calibrating the length (like a tape measure).  Another method is to measure the object first with the string, then measure  the length of string.    Ask students to get a partner and work their way through the worksheet following the directions carefully for Exercises 1-3.  In Exercise 3, make sure that students realize that they measure with a string an object that is round, and then measure the length of the string to a ruler. If you have a tape measure, that will find the length without measuring the string.     When students are finished, go over the results and guide them through Exercise 4. The answers are ft. = feet; in.= inches; cm. = centimeters; yd. = yard; mm. = millimeters; km. = kilometers; m. = meters; mi. = miles.