Conversion: 12 slices = one pizza BELLWORK 9/8/16 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 The systematic method of converting from one unit to another. Why is dimensional analysis important?
Dimensional Analysis
How Does Dimensional Analysis Work? A conversion factor is used, along with what you’re given, to determine what the new unit will be.
Examples of Conversion Factors 60 s = 1 min 60 min = 1 h 24 h = 1 day
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
Examples of Conversions Again, just be careful how you write the fraction. The fraction must be written so that like units cancel.
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.
Conversion: 365 days = one year Learning Check #1 2. How old are you in days? Given: 17 years Want: # of days Conversion: 365 days = one year
Solution Check your work… 6052 days 17 years 1 365 days 1 year X =
Conversion: 2.54 cm = one inch 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
Be careful!!! The fraction bar means divide. Solution Check your work… 6.81 inches 17.3 cm 1 1 inch 2.54 cm X = Be careful!!! The fraction bar means divide.
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 days Conversion #1: 365 days = one year Conversion #2: 24 hours = one day
Solution Check your work… 17 years 1 365 days 1 year 24 hours 1 day X = 148,920 hours
Jabberwocky Work on this problem individually. Show all of your work. Turn in your answer to me
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
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
Solution Check your work… 83 m 1 hour 0.083 km 1 hour 1000 m 1 km X = 60 min 1 min 60 sec = X X 0.023 m sec
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?