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Welcome to Physics: A college preparatory course. • Course Expectations – – – – – Cellphone = NO!!!! Need to Buy – Scientific Calculator – Notebook or Binder • • Webpage Safety Contract – Signed Warm-up HW & Review (Bonus Points) Make up missed work • • • • Notes Tests Extra Help Letters of recommendation “Are you a student, or just a kid who comes to school?” Measuring What will you study in physics (three things)? What types of jobs may require a college physics course? What is the difference between a scientist and an engineer? Measuring 1 MKS system Measuring MKS – Meter-Kilogram-Second Historical Pt-Ir meter bars U.S. National Kilogram (NIST) Seven Fundamental units Cesium Fountain Clock at NIST 1,000,000 m 1,000 m 100 m 10 m 1m 1m 1m 1m 1m = 1 Megameter (Mm) = 1 kilometer (km) = 1 hectometer (hm) = 1 dekameter (dam) = 1 meter = 10 decimeter (dm) = 100 centimeter (cm) = 1000 millimeter (mm) = 1,000,000 micrometers (mm) Kilogram Meter Second Candela Ampere Kelvin Mole Giga (G) = 109 Mega (M) = 106 kilo (k) = 103 hecto (h) = 102 deka (da) = 101 deci (d) = 10-1 centi (c) = 10-2 milli (m) = 10-3 micro (m) = 10-6 nano (n) = 10-9 pico (p) = 10-12 2 Metric Examples a. How many meters is 55 cm? b. How many milliliters is 0.0250 liters? c. How many kilograms is 13405 mg? (0.013405 kg) d. How many milliseconds is 0.0450 hectoseconds? (4500 ms) The Metric System Examples: 600 nm 0.0055 Gs 5677 kg Metric Practice Examples The Metric System Examples: 600 nm 0.0055 Gs 5677 kg 10-7 =6X m = 5.5 X 106 s = 5.67 X 106 g Metric Practice Examples a) b) c) d) e) f) g) 4658 cm 635 cm 553 ms 0.0023 kL 0.468 cm 7200 cs 10800 s = = = = = = = 0.04658 km 0.635 dam 5.53 ds 2300 mL 4.68 mm 7.2 das 3 hours =?m =?s =?g a) b) c) d) e) f) g) 4658 cm 635 cm 553 ms 0.0023 kL 0.468 cm 7200 cs 10800 s = = = = = = = ? Km ? Dam ? ds ? mL ? mm ? Das ? hours Metric Example 5 How many square meters is 685 cm2? 685 cm2 1 X 10-2 m 1 cm 685 cm2 1 X 10-2 m 1 X 10-2 m 1 cm 1 cm 685 cm2 1 X 10-2 m 1 X 10-2 m = 0.0685 m2 1 cm 1 cm 3 Metric Example 6 Metric Example 7 How many square decimeters is 0.250 m2? 0.250 m2 10 dm 1m How many cubic centimeters (cm3) is 0.00453 m3? 0.0453 m3 0.250 m2 10 dm 1m 10 dm 1m 0.250 m2 10 dm 1m 10 dm = 25.0 dm2 1m 100 cm 1m 100 cm 1m (Ans: 4530 cm3) Challenge Problem The tallest building in the world is the Burj Kalifa, Dubai. It is 828 meters tall. How many feet is that? 100 cm 1m Metric Example 9 Convert 22 miles/hour to m/s. 22 miles 1 hr 1.61 km 1X103m 1 hr 1 min = 9.8 m/s 1.00 mile 1 km 60 min 60 s (1 inch = 2.54 cm) (2717 ft) Metric Example 10 Metric Practice Examples Convert 200. cm/s to miles/hour. 200. cm 1s 1X10-2 m 1 km 1.00 mile 60 s 1 cm 1X103 m 1.61 km 1 min 60 min 1 hr 55 mi/hr 55 mi/hr 65 miles/hr 400 cm/s km/hr meters/min meters/s miles/hr = 4.47 miles/hr [1.000 mile = 1.609 km] 4 Metric Practice Examples 55 mi/hr 55 mi/hr 65 miles/hr 400 cm/s 89 km/hr 1476 meters/min 29.1 meters/s 8.94 miles/hr Accuracy and Precision Accuracy – how close the average of a set of measurements is to the true value – Measured using Percent Error Students did trials to measure the density of a metal. The accepted density is 7.2 g/cm3. Were they accurate or precise? Precision – How close a set of measured values are to one another – Measured using Range – Highest - lowest A student measures the melting point of a sample of beryllium and does four trials. The trials result in melting points of 1267 oC, 1245 oC, 1270 oC, 1255 oC. Calculate the percent error ,range and comment on accuracy and precision. (accepted = 1278 oC.) Set 1 Set 2 Set 3 7.21 7.25 7.18 6.40 7.90 7.30 6.45 6.52 6.48 A student measures the density of a sample of lead and does four trials. The trials result in densities of 11.3, 10.5, 11.9, 10.8 g/cm3. The accepted density of lead is 11.4 g/cm3. Comment on accuracy and precision by calculating the percent error and the range. 5 Hypothesis Scientific Method Hypothesis – testable, educated guess Theory Theory - repeatedly confirmed hypothesis that has predictive power. Law Law – Theory with NO known exceptions Control Vs. Experimental Groups • Control – Nothing happens to control group • Experimental – Change ONE variable Example: Plant growth Control Experimental Spotting Bad Science 1. Based on Anecdotal Evidence Anecdotal - From stories, not studies (no math) 2. Small Sample Size 3. Not published in Journals – not reviewed or tested 4. Broad Claims Example: The Water Cure 16a) 1.5 X 1011 m b) 150 Gm 32a) 0.10 nm c) 1.0 X 1010 A b) 1.0 X 105 fm d) 9.5 X 1025 A 42a) 1.00 X 109 cm3 c) 6.10 X 107 in3 b) 3.53 X 104 ft3 SCIENCE IS REPRODUCIBLE 6 • http://theuniverseandmore.com/ • http://phet.colorado.edu/en/simulation/movin g-man • http://jersey.uoregon.edu/block/Block.html • http://www.cabrillo.edu/~dbrown/tracker/ A 250 cm G 5.678292 km M 3.15 X 107 S 2153 ft2 s B 420 mm H 1.2 cm N 29.1 m/s C 46.7 m I D 0.500 A J 2470 cm E 5.5 X 10-7 m K 2.68 X 109 Q 516 cm2 s F 3.11 miles L 4.8 cm 0.0862 km O 62.1 mph P 78.3 mph T 18.6 m2 U 6540 yd3 V 61.0 in3 R 0.052 m2 List three specific things TO DO to be academically successful in this course. List three things NOT TO DO (academically) in this course 7