Physical Quantities and Units.

1. Mass

1.1. SI unit is kilogram

1.2. measured with an electronic beam blalnce

1.2.1. accuracy of 0.1 grams

1.3. mass and weight are diffferent

1.3.1. different quantities

1.3.2. different units

1.3.3. different instruments to measure them

2. Time

2.1. SI unit is second

2.1.1. the second is defined as 9192631700 times the period of oscillation of radiation from the cesium atom

2.2. a digital stopwatch is usually used to measure short time intervals

2.2.1. accuracy of +- 0.01 s

2.2.2. more accurate than an analogue stopwatch (0.1 s)

2.2.3. Human reaction error of about 0.3s for most people

3. Physical quantities and Bass unit

3.1. Length( metre)

3.2. mass (kilogram)

3.3. time (second)

3.4. Electric current ( ampere)

3.5. Thermodynamic temperature ( kelvin)

3.6. Luminous intensity ( candela)

3.7. Amount of substance (mole)

4. Length

4.1. In 1799 the legal standard of lenght in france became the metre, defined as one ten-millionth of the distance from the euqator to the pole.

4.2. instruments: metre rule

4.2.1. its is the most commonly used instruments for the measurement of length.

4.3. instruments: vernier calipers

4.3.1. the vernier calipers is used to measure length up to an accuracy of 0.01cm

4.4. instruments: microwave screw guage

4.4.1. http://www.youtube.com/watch?v=oHqaLMEHlnE

4.4.2. used to measure length up to an accuracy of +- 0.001cm.

5. Prefixes and Units

5.1. tera

5.1.1. T

5.2. giga

5.2.1. G

5.3. mega

5.3.1. M

5.4. kilo

5.4.1. k

5.5. hecto

5.5.1. h

5.6. deka

5.6.1. da

5.7. deci

5.7.1. d

5.8. centi

5.8.1. c

5.9. milli

5.9.1. m

5.10. micro

5.10.1. u

5.11. nano

5.11.1. n

5.12. pico

5.12.1. p

5.13. femto

5.13.1. f