Physical Quantities and Units

Physical Quantities and Units
SecondDefined as: 9.192.631,700 times the
period of oscillation of radiation from the
cesium atom
Digital Stopwatch used to
measure short time intervals
Accurate to +/0.01 s
Analogue Stopwatch
Accurate to +/0.1 s
Human reaction error when using stopwatch
0.3 s incurred
Mechanical instruments:
watches/ticker-tape timers
Use repetitive motion/vibrations
Known asOscillations
Time to complete 1 Oscillation=
Period of oscillation
Length / metre / m
Mass / kilogram / kg
Time / second / s
Physical Quantity /Base Unit/ Symbol
Electric Current / ampere / A
Temperature / kelvin / K
Luminous intensity/ candela/ Cd
Amt of Substance / mole/ mol
SI UnitKilogram (KG)
measured via Electronic Beam
Balance/ Sliding Balance
Mass and Weight are NOT the Same!
Prefixes in units
To express numbers involving decimals
1012 tera T
109 giga G
106 mega M
103 kilo k
102 hecto h
101 deka da
Factor Name Symbol
10-1 deci d
10-2 centi c
10-3 milli m
10-6 micro µ
10-9 nano n
10-12 pico p
10-15 femto f
Metrelength of the path travelled by light in a
vacuum during a time interval of 1/299792458 of
a second.
Metre Rule
Accurate to 0.001 m
( 1 millimeter)
Venier Calipers
Accurate to +/0.01cm
Inside jaws to measure interiors diameters
Outside jaws to measure exterior diameters
Tail to measure depths
Micrometer Screw Gauge
Accurate to +/0.001 cm