Dimensional Analysis

2. Dimensional Analysis Why do it? Kat Woodring

3. Benefits for students • Consistent problem solving approach • Reduces errors in algebra • Reinforces unit conversion • Simplifies computation • Improves understanding of math applications • Multiple ways to solve the same problem

4. 5 Steps of Dimensional AnalysisUsing the Metric Conversion • Start with what value is known, proceed to the unknown. • Draw the dimensional lines (count the “jumps”). • Insert the unit relationships. • Cancel the units. • Do the math, include units in answer.

5. Write the KNOWN, identify the UNKNOWN. • EX. How many quarts is 9.3 cups? 9.3 cups = ? quarts

6. 9.3 cups = ? quarts Draw the dimensional “jumps”. 9.3 cups x * Use charts or tables to find relationships

7. Insert relationship so units cancel. quart 1 9.3 cups x 4 cups *units of known in denominator (bottom) first *** units of unknowns in numerator (top

8. 1 quart 9.3 cups x 4 cups Cancel units

9. 1 quart 9.3 cups x 4 cups Do Math • Follow order of operations! • Multiply values in numerator • If necessary multiply values in denominator • Divide.

10. 9.3 = 4 Do the Math 1 quart 9.3 x 1 9.3 cups x = 4 cups 1 x 4 = 2.325 s

11. Vocabulary • KNOWN • UNKNOWN • CONVERSION FACTOR • UNITS

12. Initial and Final Units 1. A person has a height of 2.0 meters. What is that height in inches? Initial unit = m Final unit = _______ 2) Blood has a density of 0.05 g/mL. If a person lost 0.30 pints of blood at 18°C, how many ounces of blood would that be? Initial = pints Final unit = _______ LecturePLUS Timberlake

13. How many minutes are in 2.5 hours? Initial unit 2.5 hr Conversion Final factor unit 2.5 hr x 60 min = 150 min 1 hr cancel Answer (2 SF) LecturePLUS Timberlake

14. Learning Check An adult human has 4650 mL of blood. How many gallons of blood is that? Unit plan:mL qt gallon Equalities: 1 quart = 946 mL 1 gallon = 4 quarts Your Setup: LecturePLUS Timberlake

15. Solution Unit plan:mL qt gallon Setup: 4650 mL x 1 qt x 1 gal = 1.23 gal 946 mL 4 qt 3 SF 3 SF exact 3 SF LecturePLUS Timberlake

16. Write the KNOWN, identify the UNKNOWN. • EX. How many km2 is 802 mm2 ? 802 mm2 = km2?

17. 802 mm2 = km2? Draw the # of dimensional “jumps” 802 mm2 x x x x x x

18. 802 mm2 = km2? Insert Relationships cm2 dm2 m2 dkm2 hm2 km2 802 mm2 x x x x x x mm2 cm2 dm2 m2 dkm2 hm2

19. cm2 dm2 m2 dkm2 hm2 km2 802 mm2 x x x x x x mm2 cm2 dm2 m2 dkm2 hm2 Cancel Units *Units leftover SHOULD be units of UNKNOWN

20. cm2 dm2 m2 dkm2 hm2 km2 x x x x x x mm2 cm2 dm2 m2 dkm2 hm2 Cancel Units (1)2 (1)2 (1)2 (1)2 (1)2 (1)2 802 mm2 (10)2 (10)2 (10)2 (10)2 (10)2 (10)2 *Units leftover SHOULD be units of UNKNOWN

21. cm2 dm2 m2 dkm2 hm2 km2 x x x x x x mm2 cm2 dm2 m2 dkm2 hm2 Do the Math… (1)2 (1)2 (1)2 (1)2 (1)2 (1)2 802 mm2 (10)2 (10)2 (10)2 (10)2 (10)2 (10)2 *What kind of calculator is BEST?

22. Differences from other math approaches • Solve for variables in equation first, then substitute values • Open ended application • No memorized short-cuts • No memorized formulas • Reference tables, conversion factors encouraged