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Unit Conversions

Unit Conversions. 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

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Unit Conversions

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  1. Unit Conversions

  2. Objective • Convert between different SI units • Convert English units to SI units

  3. 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

  4. Agenda • Do Now • Heart of the Lesson #1 – Dimensional Analysis • Summary • HW: 1.11 HW Dimensional Analysis + review questions Get gradesheet signed Quiz tomorrow

  5. Conversion factors…in our lives

  6. Conversion Factor: • Factor equal to 1 • Use it to convert from one unit to another

  7. Dimensional Analysis: • Problem-solving method that uses conversion factors to convert between units • Not changing the value of the measurement, only the units

  8. BIG IDEA #1 for Dimensional Analysis • 4/4 = 1 • 10/10 = 1 • x/x = 1 • BIG IDEA #1: any value divided by itself = 1

  9. Example 24 hours = 1 day = = 1 The conversion factor is equal to 1 (any value divided by itself = 1)

  10. 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

  11. 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

  12. 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

  13. 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

  14. Conversion factor: Multiply orig. measurement by the conversion factor: 3 m x

  15. 3 m x 3 m x 3 x 100 cm = 300 cm There are 300 cm in 3 meters

  16. 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

  17. Divide by the conversion factors: and 250 s x x

  18. 250 s x x 250 s x x hr = .0694 hr There are .0694 hours in 250 seconds

  19. 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

  20. Gradesheets • Grading Policy • Quizzes – 25% • Interim Assessments – 20% • Tests – 15% • Homework – 15% • Classwork – 10% • Labs & Projects – 10% • Participation – 5%

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