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BELLWORK 8/18/17

BELLWORK 8/18/17. Suppose there are 12 slices of pizza in one pizza. How many slices are in 7 pizzas?. Given: 7 pizzas Want: # of slices Conversion: 12 slices = one pizza. Solution. Check your work…. 84 slices. 7 pizzas 1. 12 slices 1 pizza. X. =. Dimensional Analysis.

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BELLWORK 8/18/17

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  1. BELLWORK 8/18/17 • Suppose there are 12 slices of pizza in one pizza. How many slices are in 7 pizzas? Given: 7 pizzas Want: # of slices Conversion: 12 slices = one pizza

  2. Solution • Check your work… 84 slices 7 pizzas 1 12 slices 1 pizza X =

  3. Dimensional Analysis • The systematic method of converting from one unit to another. • Why is dimensional analysis important?

  4. Dimensional Analysis

  5. How Does Dimensional Analysis Work? • A conversion factor is used, along with what you’re given, to determine what the new unit will be.

  6. How Does Dimensional Analysis Work? • If we write these expressions mathematically, they would look like 3 cm = 50 km

  7. Examples of Conversion Factors • 60 s = 1 min • 60 min = 1 h • 24 h = 1 day

  8. Examples of Conversions • You can write any conversion factors as fractions. For example, you can write: 60 s = 1 min as 60s or 1 min 1 min 60 s

  9. Examples of Conversions • Again, just be careful how you write the fraction. • The fraction must be written so that like units cancel.

  10. Steps • Start with the given value. • Write the multiplication symbol. • Choose the appropriate conversion factor. • The problem is solved by multiplying the given data & their units by the appropriate unit factors so that the desired units remain. • Remember, cancel like units.

  11. Learning Check #1 2. How old are you in days? Given: 17 years Want: # of days Conversion: 365 days = one year

  12. Solution • Check your work… 6.205 x 103days 17 years 1 365 days 1 year X =

  13. Learning Check #2 3. There are 2.54 cm in one inch. How many inches are in 17.3 cm? Given: 17.3 cm Want: # of inches Conversion: 2.54 cm = one inch

  14. Solution • Check your work… 6.81 inches 17.3 cm 1 1 inch 2.54 cm X = Be careful!!! The fraction bar means divide.

  15. Multiple-Step Problems • Most problems are not simple one-step solutions. Sometimes, you will have to perform multiple conversions. • Example: How old are you in hours? Given: 17 years Want: # of hours Conversion #1: 365 days = one year Conversion #2: 24 hours = one day

  16. Solution • Check your work… 17 years 1 365 days 1 year 24 hours 1 day X X = 148,920 hours

  17. Jabberwocky • Work on this problem individually. • Show all of your work. • Turn in your answer to me

  18. Combination Units • Dimensional Analysis can also be used for combination units. • Like converting km/h into cm/s. • Write the fraction in a “clean” manner: km/h becomes km h

  19. Combination Units • Example: Convert 0.083 km/h into m/s. Given: 0.083 km/h Want: # m/s Conversion #1: 1000 m = 1 km Conversion #2: 1 hour = 60 minutes Conversion #3: 1 minute = 60 seconds

  20. Solution • Check your work… 83 m 1 hour 0.083 km 1 hour 1000 m 1 km X = 83 m 1 hour 1 hour 60 min 1 min 60 sec = X X 0.023 m sec

  21. Crash of Flight 143 • Watch this video and answer the following questions. • 1. What was the cause of the Crash of Flight 143? • 2. How does this relate to the importance of using dimensional analysis?

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