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Which one of these images show a place where it is 32 degrees? How do you know?

Either go to socrative.com in safari and click student login or open the socrative app on your iPad Enter the 659644 as the room number You will have 15 minutes to complete the quiz. Which one of these images show a place where it is 32 degrees? How do you know?. 2. 1. 3. Unit Conversions.

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Which one of these images show a place where it is 32 degrees? How do you know?

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  1. Either go to socrative.com in safari and click student login or open the socrative app on your iPad • Enter the 659644 as the room number • You will have 15 minutes to complete the quiz.

  2. Which one of these images show a place where it is 32 degrees? How do you know? 2 1 3

  3. Unit Conversions

  4. Why Units Important "The 'root cause' of the loss of the spacecraft was the failed translation of English units into metric units in a segment of ground-based, navigation-related mission software, as NASA has previously announced," said Arthur Stephenson, chairman of the Mars Climate Orbiter Mission Failure Investigation Board. "The failure review board has identified other significant factors that allowed this error to be born, and then let it linger and propagate to the point where it resulted in a major error in our understanding of the spacecraft's path as it approached Mars." http://mars.jpl.nasa.gov/msp98/orbiter/ 4

  5. Conversion factors • Conversion factors are built from an equivalence statement which shows the relationship between the units in different systems. 1 inch = 2.54cm or 1 cm = 0.394 inches • Conversion factors are ratios of the two parts of the equivalence statement that relate the two units. 1 inch or2.54cmor0.394 inchesor 1 cm . 2.54cm 1 inch 1 cm 0.394 inches

  6. 1 ft ______ 1 ft 12 in 12 in ( ) ______ 12 in ____ 1 ft 3.28 ft equality: 1 ft = 12 in How many feet is 39.37 inches? applicable conversion factors: or X ft = 39.37 in = We use the idea of unit cancellation to decide upon which one of the two conversion factors we choose.

  7. in3 L B. Dimensional Analysis • How many liters of water would fill a container that measures 75.0 in3? 1 L 1000 cm3 (2.54 cm)3 (1 in)3 75.0 in3 = 1.23 L

  8. ______ 100 cm 100 cm 1 m ______ 1 m 1 m 100 cm ______ 132 cm ( ) equality: 1 m = 100 cm (or 0.01 m = 1 cm) How many cm are in 1.32 meters? applicable conversion factors: or X cm = 1.32 m = Again, the units must cancel.

  9. L W Measured dimensions of a rectangle: length (L) = 9.70 cm width (W) = 4.25 cm Find area of rectangle. A = L . W = (9.70 cm)(4.25 cm) = 41.2 cm 2 . cm

  10. ( ( ( ( ) ) ) ) ______ ______ ______ ______ 1 m 1 m 1 m 1 m 100 cm 100 cm 100 cm 100 cm 2 X m2 = 41.2 cm2 = 0.412 m2 WRONG! Convert 41.2 cm2 to m2. Remember: Treat your units as if they are variables in math, if they have an exponent so must your conversion factor = 0.412 cm.m Recall that… 41.2 cm2 = 41.2 cm.cm X m2 = 41.2 cm.cm = 0.00412 m2 X m2 = 41.2 cm2 = 0.00412 m2

  11. What if I have 2 units in my measurement? Problem: The permeability of sand is 1.0x10-4cm/s. If a chemical herbicide is dumped on a sandy soil, how long (in hours) will it take for the contaminant to reach the well 150 feet away. Diagram: 150 feet Herbicide Well Permeability of Sand = 1.0x10-4 cm/s t = Time (hours) 1.0x10-4 cm/s = __?__ ft/hr

  12. What if I have 2 units in my measurement? Theory: Permeability = Distance/Time Assumptions: Sand has constant permeability in area Herbicide moves per permeability of sand Solution: 1 in 1 ft 60 s 60 min 1.0x10-4 cm s 2.54 cm 12 in 1 min 1 hr = 0.011811 ft/hr

  13. Summary: Tools for Problem Solving • Step 1 Find an equivalence statement that relates the 2 units. • Step 2 Choose the conversion factor by looking at the direction of the required change (cancel the unwanted units). • Step 3 Multiply the original quantity by the conversion factor. • Step 4 Make sure you have the correct number of significant figures.

  14. NUMBER = UNIT Think of conversion factors as a scale 0.532 532 m = _______ km NUMBER UNIT

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