1. We will have our first test in 3. 3 WHAT!! Without units it is a meaningless statement! All measurements require a unit – otherwise the measurement is wrong!

2. Fundamental & Derived Units

3. Dimensions & Units Dimensions tell what physical property you are measuring like time, space, volume. Units say something about the amount you are measuring. Small distance mm, large distance km.

4. 7 Base/Fundamental Units Physics UnitSymbol DimensionDefinition Meterm length Kilogramkg mass__________. Second___time__________. Ampere___charge rate elc charge flow. KelvinK________________.

5. Derived Units: Combos of base Mechanics – motion, force, matter. All units derived from kg, m, s. Ex: density, velocity.

6. Remind yourselves of the metric prefixes. Ref Tables. 10 12 g = ___ g. ____m = 1 pm 9  m=____m. 10 12 g = 1 Tg (Tera). 1x10 -12 m = 1 pm (pico) 9  m= 9 x 10 -6 m (micro).

7. Practice. 13 Ghz 22 Mp 1.3 dm 15 mJ 13 x 10 9 hz 22 x 10 6 p 1.3 x 10 -1 m 15 x 10 -3 J

8. Text pg 27 #5

9. Dimensional Analysis Used to convert between units and prefixes. The method makes use of multiplying by unit factors to complete conversions.

10. Unit Factors are fractions = 1 We use them as multiplier. Tx pg 12. 1 cm/10 -2 m 10 -2 m/1cm. 10 -3 g/1 mg. 1mg/1x10 -3 g. All equal the number 1. It doesn’t matter which is in numerator.

11. Use the method for unit conversion Handout “Dimensional Analysis” Review. Do wksht prac dimensional analysis problems together.

12. Video Lesson Metric Prefixes & Conversions https://www.youtube.com/watch?v=LaLXN2D xQN4 https://www.youtube.com/watch?v=LaLXN2D xQN4 Hwk. Text pg 28 #11 a-g. Show all work.

13. Do Now:

14. Order of Magnitude & Estimation Physics must give values for the very large & the very small. The prefixes give orders of magnitude (power of 10) to the value.

15. Order of Magnitude All numbers can be expressed as a power of 10. O.M. refers to the power of 10 to which a measurement is closest. The number 2 is between 10 0 = 1 and 10 1 = 10 but closer to 1. OM =10 0. 3 cm = 0.03 m between 0.1 - 0.01 10 -1 – 10 -2 m Closer to 10 -2.

16. 2 km in meters = 2 x 10 3 m or 2000 m. order of magnitude in meters is 10 3. 1.4  g = 1.4 x 10 -6 g. OM grams is ___________. 10 -6. We say “on the order of 10 -6 grams.

17. Some orders of magnitude are easy. In meters: 100 m = 1x 10 2 m. 2 mm = 2x 10 -3 m. 30 cm = 30 x 10 -2 m = 3.0 x 10 -1 m If the coefficient is between 4 – 6 it’s harder. Your calculator will do it right!

18. 127 m 488 g 420 nm in m We can use the log function on your calculator to find the order of magnitude. Then round the answer. 10 2.1 ~ 10 2 10 2.688 ~ 10 3 420 x 10 -9 ~ 10 -6.3767 ~ 10 -6. Using the log function, find the order of magnitude for the following:

19. 2. What is the order of magnitude of the distance in meters from Earth to the moon? 10 9 m.

20. 3. Estimate the order of magnitude of the height of the counter in cm. 100 cm ~ 10 2 cm. 4. Estimate the order of magnitude of the thickness of a pencil tip in meters. 1 mm = 10 -3 m

21. Hwk: Worksheet Order Magnitude Estimation

22. Fermi Estimations 4 min https://www.youtube.com/watch?v=0YzvupO X8Is https://www.youtube.com/watch?v=0YzvupO X8Is