1. Physics Day 4 AIM: How do we measure things? LO: SI units and prefixes LO: Dimensional Analysis aka Factor Label Method LO: Scientific Notation AGENDA Do Now Notes on Units Worksheet HW02 due 9.8 Do Now 1/ Collect a Reference Table 2/ Pick up a Physics Work Book and put your name on it. 3/ Open the workbook and read the first two pages.

2. Mathematical Concepts Units: Unit conversion, Dimensional Analysis Trigonometry

3. Units System SICGSBE SI stands for the French phrase "Le Systeme International d'Unitus." CGS - centimeter (cm), gram (g), and second. BE - British Engineering.

4. Units System SICGSBE Lengthmeter (m)centimeter (cm)foot (ft) SI stands for the French phrase "Le Systeme International d'Unitus." CGS - centimeter (cm), gram (g), and second. BE - British Engineering.

5. Units System SICGSBE Lengthmeter (m)centimeter (cm)foot (ft) Masskilogram (kg)gram (g)slug (sl) SI stands for the French phrase "Le Systeme International d'Unitus." CGS - centimeter (cm), gram (g), and second. BE - British Engineering.

6. Units System SICGSBE Lengthmeter (m)centimeter (cm)foot (ft) Masskilogram (kg)gram (g)slug (sl) Timesecond (s) SI stands for the French phrase "Le Systeme International d'Unitus." CGS - centimeter (cm), gram (g), and second. BE - British Engineering.

7. Units of length Early units of length were associated with the human body.

8. Units of length Early units of length were associated with the human body. The foot was originally defined to be the length of the royal foot of King Louis XIV.

9. Units of length Early units of length were associated with the human body. The foot was originally defined to be the length of the royal foot of King Louis XIV. These units are not reproducible.

10. Earlier Definition of meter Metre (meter) originated from the Greek word metron meaning “measure”.

11. Earlier Definition of meter Metre (meter) originated from the Greek word metron meaning “measure”. In 1793, the meter was defined in terms of the distance measured along the earth's surface between the north pole and the equator.

12. Standard Meter Bar In 1799, a platinum-iridium meter bar, was used to define meter.

13. Standard Meter Today Since 1983, meter is defined using the speed of light, 299 792 458 m/s. The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.

14. Standard Kilogram Today The standard platinum-iridium kilogram is kept at the International Bureau of Weights and Measures in Sevres, France.

15. Units of time The Earth takes 24 hours to rotate once. Before 1956, the mean solar day was defined to be 24x60x60 = 86,400 seconds.

16. Standard Second Today The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. A cesium atomic clock.

17. Physical Quantity Unit NameSymbol Timeseconds Lengthmeterm Masskilogramkg Electric currentampereA TemperaturekelvinK Amount of substance molemol Luminous intensity candelacd SI Base Units

18. Some SI Derived Units Area-m 2 Volume -m 3 Density-kg/m 3

19. Sine, Cosine, and Tangent

22. Pythagorean Theorem

23. Dimensional Analysis –A systematic method for solving problems in which units are carried thru the entire problem units are multiplied together, divided into each other, or cancelled –Helps ensure that problems are solved correctly –Helps ensure that solutions have the proper units –Uses conversion factors

24. Conversion Factors Conversion Factor –a fraction whose numerator and denominator are the same quantity expressed in different units –used to change from one unit to another

25. Conversion Factors Examples of Conversion Factors 12 in = 1 ft 100 cm = 1 m 12 in or 1 ft 1 ft 12 in 100 cm or 1 m 1 m 100 cm Every relationship can give two conversion factors that are the inverses of each other.

26. Dimensional Analysis - One Conversion Factor Example: A lab bench is 175 inches long. What is its length in feet?

27. Given:175 in. Find:Length (ft) Conversion factor: 12 in or 1 ft 1 ft12 in. ft = 175 in X 1 ft = 14.583333 ft = 14.6 ft 12 in Dimensional Analysis - One Conversion Factor

28. Example: A marble rolled 50.0 mm. How many meters did it roll?

29. Conversion factor: 1000 mm or 1 m 1 m 1000 mm Dimensional Analysis - One Conversion Factor Example: A marble rolled 50.0 mm. How many meters did it roll? Given:50.0 mm Find:dist. (m) m = 50.0 mm X 1 m = 0.05 m = 0.0500 m 1000 mm

30. Dimensional Analysis - One Conversion Factor Example: In Germany, a salesman I was with drove at 185 km/hr. What was our speed in mi/hr?

31. Dimensional Analysis - One Conversion Factor Example: In Germany, a salesman I was with drove at 185 km/hr. What was our speed in mi/hr? Conversion factor: 1.609 km or 1 mi 1 mi 1.609 km Given:185 km/hr Find:mi/hr mi = 185 km X 1 mi = 114.97825 mi hrhr1.609 kmhr Speed = 115 mi/hr

32. Exponentials