SI System of Units Chapter 13

Background SI System of Units = “metric system” Used worldwide except in US, Liberia, Burma Old Units Bushel = 8 Gallons Stone =14 pounds Cubit = Length of the Pharaoh’s elbow to fingertip Hand = 4 inches Fortnight = 2 weeks

3 History of the Meter? Delambra and Mechain 1792 to 1799 “quadrant of meridian” Pole to Equator of Earth -> 10 million parts Scratches on Platinum Bar Resurvey… 10,002,288.3 meters

4 SI Units MKS meters, kilograms, seconds CGS centimeters, grams, seconds Miles? 1 mile = 5280 ft 1 nautical mile = 1852 m

5 Exercise Give the MKS and CGS units for the following: 1. Volume 2. Acceleration 3. Density 4. Force 5. Energy 6. Speed 7. Orbital Period 8. Frequency 9. Angular Velocity

6 Multiples and Prefixes tera (T) giga (G) mega (M) kilo (k) milli (m) micro (  ) nano (n) pico (p) Prefix Rule Use a prefix that will give you 1, 2, or 3 digits to the left of the decimal.

7 Exercise Use the “prefix rule” to rewrite each measurement 1.485,684 m g × 10 5 Hz × 10 8 Hz × A 6.7,300,000 V m/s

8 Exercise Round the following numbers to three significant figures , ,001

9 Exercise Write each of the following in scientific notation. 1.( m)/(558 sec) 2.(248287in 2 )(1ft/12 in) 2 3.(452 m)(12000 N) 4.(1,000,000 cycles)/(153 seconds) 5.(2  radians)/(6.02 seconds)

10 Problems 13.1 and (a) 18.3 Newton (b) 45.6 n (c) 29.0 meter (d) 56.9 meter/sec (e) five m (f) 23 m/second (g) 493°K (h) 89.6  m (i) 68.5 Kg (j) 98.4 m/s/s (k) 10 m’s (l) Mm/ms 13.1 (a) 18.3 N (b) 45.6 N (c) 29.0 m (d) 56.9 m/s (e) 5 m (f) 23 m/s (g) 493 K (h) 89.6  m (i) 68.5 kg (j) 98.4 m/s 2 (k) 10 m·s (l) 1000 m/s

11 Problems 13.1 and (a) 9.8 x 10 5 m (b) 9.56 x J (c) s (d) 1,984,000 m 3 (e) 35.6 x g (f) 92.4 x 10 7 N 13.2 (a) 980 km (b) 95.6 GJ (c) 56  s (d) Mm 3 (e) 3.56 mg (f) 924 MN

Unit Jeopardy SPS

Jet Propulsion Laboratory, Pasadena, CA RELEASE MARS CLIMATE ORBITER TEAM FINDS LIKELY CAUSE OF LOSS “A failure to recognize and correct an error in a transfer of information between the Mars Climate Orbiter spacecraft team in Colorado and the mission navigation team in California led to the loss of the spacecraft, preliminary findings by NASA's Jet Propulsion Laboratory internal peer review indicate.” “The peer review preliminary findings indicate that one team used English units (e.g., inches, feet and pounds) while the other used metric units for a key spacecraft operation. This information was critical to the maneuvers required to place the spacecraft in the proper Mars orbit.” Uh oh…