Zusammenfassung der Ressource
Measurement
- physical quantity
- quantity that can be measured
- numerical magnitude & a unit
- SI units
- prefixes
- 10^9 (G, giga-)
- 10^6 (M, mega-)
- 10^3 (k, kilo-)
- 10^-1 (d, deci-)
- 10^-2 (c, centi-)
- 10^-3 (m, milli-)
- 10^-6 (micro-)
- 10^-9 (n, nano-)
- 7 base quantities
- #mass
- kilogram (kg)
- #time
- second (s)
- stopwatches
- precision to 0.1s
- pendulum
- period
- time taken for one complete oscillation
- swing from one end to the other and back again to starting position
- oscillation
- each complete to-and-fro motion
- human reaction time
- #electric current
- ampere (A)
- #temperature
- kelvin (K)
- luminous intensity
- candela (cd)
- amount of substance
- mole (mol)
- #length
- metre (m)
- metre rule
- avoid parallax errors
- precision to 0.1cm; length of a book
- vernier calipers
- main scale & sliding vernier scale
- check for zero error
- positive/ negative
- how to read?
- 1. grip object gently using outside jaws of calipers
- 2. read main scale opp. zero mark on vernier scale
- 3. find the mark which coincides with a marking on main scale
- 4. find diameter by adding main scale reading to vernier scale reading
- precision to 0.01cm; diameter of a test-tube
- micrometer screw gauge
- how to read?
- 1. turn thimble until the anvil and spindle gently grip the object, turn until ratchet clicks
- 2. read main scale reading at edge of thimble
- 3. thimble scale has 50 divisions, each is 0.01mm. take thimble reading opposite datum line of main scale
- 4. find diameter by adding main scale reading to thimble reading
- precision to 0.01mm; wires
- check for zero error
- positive/ negative
- tape measure
- precision to 0.1cm; a person's waist
- derived quantities
- area
- length*width (m^2)
- volume
- length*width*height (m^3)
- speed
- length/time (ms^-1)