Physical quantities, units and measurements

base quantities and their units:

mass → kg (kilogram)

length → m (metre)

Time → s (second)

Electric current → A (amphere)

Thermodynamic Temperature → K (kelvin)

Amount of substance → mol (mole)

Prefixes + Symbols

tera - 10^12

giga - 10^9

mega - 10^6

kilo - 10^3

deci - 10^-1

centi - 10^-2

mili - 10^-3

micro 10^ -6

nano - 10 ^-9

Magnitude of sizes of common objects

size of an atom → 10^-10m

radius of the earth → 6,378,000m

select and explain the use of appropriate measuring instruments to measure or determine physical quantities taking into consideration the range and precision of the instrument (length)

Tape measure - 0.1cm

Metre rule - 0.1cm

digital calipers - 0.001cm (1 to 15cm)

digital micrometer screw gauge - 0.0001cm (less than 2.5cm)

state what is meant by scalar and vector quantities and give common examples

Scaler → Physical quantities which have magnitude only

Vector → Physical quantities which have magnitude and direction