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Measurement Tools and Readings Determining submarkings • Every submark on a tool is not labeled, so you must be able to determine the quantity it represents. What does each of the small divisions represent below? 10 20 30 40 50 What does each of the small divisions represent below? 10 20 30 40 50 There is a magnitude difference of 10 units between each marking. There are 10 divisions between each marking. Therefore, each subdivision = 1 unit. 10 units 10 divisions = 1unit/division The general rule for determining the value of a subdivision is: difference between adjacent marks = # of units per division # of divisions between adjacent marks Try these: 10 30 50 70 90 20 units/ 10 divisions = 2 units/division 10 11 12 13 14 1 unit/ 10 divisions = .1 units/ division 1 2 3 4 1 unit / 4 divisions = .25 units/division 5 The math symbol “/ ” means divided by. In words, “ / “ is said “per”. So, 3 km/hr would be said “three kilometers per hour”. Why is this skill important? Determining the true value of submarkings enables you to take accurate measurements. Your data is then accurate. AND Calculations and conclusions are meaningful. Now try these: 10 20 30 40 10 units/ 4 divisions = 2.5 units/division 50 10 50 20 30 40 10 units/ 5 divisions = 2 units/division 10 11 12 13 1 units/ 5 divisions = .2 units/division 14 Now let’s read measurements. 46 units 10 30 50 70 90 1.9 units 10 11 12 13 14 2.75 units 1 2 3 4 5 One Last Time: 26 units 10 20 30 40 50 30 40 50 9 units 10 20 2.1 units 10 11 12 13 14 Common Mistake • Reading the inch markings are not the same as in metric. • There are NOT 10 divisions in each inch. • There are 16 divisions!! • One division = 1/16 = .0625 NOT 0.1 Read the length: 1 2 3 The length is 1 3/16 inch = 1.1875 inch. It is NOT 1.3 inch! inch Tools • Ruler/ Meter stick – length • Graduated cylinder – volume • Thermometer – temperature • Balance – mass • Stopwatch/ Ticker Tape Machine - time Reading a balance 1. Move all the riders (sliding masses) to the left. 2. Adjust the balance so that it zeros. 3. Move heaviest rider gradually to the right, notch by notch, until the balance dips then back up one notch to the left. 4. Use the same procedure for the remaining riders, going heaviest to lightest. 5. Add up all the rider values to determine mass. Read the mass indicated below: 0 0 0 0 0.1 100 10 20 30 40 50 1 2 3 4 5 0.2 0.3 0.4 200 60 70 6 0.5 7 0.6 80 90 100 8 9 10 0.7 100 + 80 + 3 + .47 = 183.47 g 0.8 0.9 1.0 g It is important to know how to determine the value of a subdivision or submarking! difference between adjacent marks # of divisions between adjacent marks = # of units per division