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## Unit Conversions

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**Objective**• Convert between different SI units • Convert English units to SI units**Real World Example**• Mars climate orbiter in 1999 • Engineers at Lockheed Martin using US system for units • Engineers at NASA using SI system for units Led to explosion of the Mars orbiter and loss of $125 million**Agenda**• Do Now • Heart of the Lesson #1 – Dimensional Analysis • Summary • HW: 1.11 HW Dimensional Analysis + review questions Get gradesheet signed Quiz tomorrow**Conversion Factor:**• Factor equal to 1 • Use it to convert from one unit to another**Dimensional Analysis:**• Problem-solving method that uses conversion factors to convert between units • Not changing the value of the measurement, only the units**BIG IDEA #1 for Dimensional Analysis**• 4/4 = 1 • 10/10 = 1 • x/x = 1 • BIG IDEA #1: any value divided by itself = 1**Example**24 hours = 1 day = = 1 The conversion factor is equal to 1 (any value divided by itself = 1)**BIG IDEA #2 for Dimensional Analysis**• 4 x1 = 4 • 10 x 1 = 10 • y x 1 = y • BIG IDEA #2: any value multiplied by 1 has the same value**Example #1**How many centimeters are in 1 meter? 100 Definition of a centimeter: 1 cm = 10-2 m Conversion factor: 102 cm = 1 m 100 cm = 1 meter**How many centimeters are in 3 meters?**• Are centimeters bigger or smaller than meters? Smaller • For any number of meters, I will have more centimeters • So in 3 meters, will I have more or less than 3 centimeters? More**For any number of meters, I will have more centimeters**• Since I want the final number to bebigger, I have to multiply the original measurement by the conversion factor**Conversion factor:**Multiply orig. measurement by the conversion factor: 3 m x**3 m x**3 m x 3 x 100 cm = 300 cm There are 300 cm in 3 meters**Example #2: How many hours are equivalent to 250 seconds?**Conversion factors: 60 min = 1 hr 60 sec = 1 min • Are hours bigger or smaller than seconds? Bigger For any number of seconds, I will have fewer hours • Since I want the final number to be smaller, I have to divide the original measurement by the conversion factor**Divide by the conversion factors:**and 250 s x x**250 s x x**250 s x x hr = .0694 hr There are .0694 hours in 250 seconds**Summary**• If you want the final answer to be bigger, you multiply by the conversion factor • If you want the final answer to be smaller, you divide by the conversion factor • The value is the same, but the units change • Conversion factor is what you use to convert from one unit to another • Dimensional analysis is a way to convert btwn 2 diff units**Gradesheets**• Grading Policy • Quizzes – 25% • Interim Assessments – 20% • Tests – 15% • Homework – 15% • Classwork – 10% • Labs & Projects – 10% • Participation – 5%