PHYSICAL QUANTITIES
SI (System International) system of units: 7 base quantities w/ fundamental units which are arbitrary
| QUANTITY | SI UNIT
|
|---|
| length | metre, m
|
| mass | kilogram, kg
|
| time | second, s
|
| electric current | amperes, A
|
| temp | kelvin, K
|
| amt of subs | mole, mol
|
| luminous intensity | candela, cd
|
physical quantity = measurable feature if diff items, has numerical value and unit
some phys quantity don't have units (quotient of 2 terms w/ same unit > unit cancelled; relative)
from fundamental units all other physical quantities can be derived (speed, m/s)
SI system based of multiples of 10 > metric
| POWER | PREFIX | SYMBOL
|
|---|
| 1012 | tera | T
|
| 109 | giga | G
|
| 106 | mega | M
|
| 103 | kilo | k
|
| 10-2 | centi | c
|
| 10-3 | milli | m
|
| 10-6 | micro | µ
|
| 10-9 | nano | n
|
| 10-12 | pico | p
|
A dimension- expressions of a phys quan's/units in terms of base quan's/units
Dimensions placed in '[..]' [M]-mass, [L]-length, [T]-time, [I/A]-elec current, [q]-temp, [N]-# of moles, [I]-luminous intensity
Dimension check homogeneity of phys equation- both sides of equation must have equal dimensions
Avogadro's constant; numerical = to # of atoms in 0.012kg of 12C (ie 6.02217 x 1023 mol-1)
1 mole of subs = amt containing # of particles = to # atoms in 0.012kg of 12C (ie 6.02217 x 1023 particles/mol)
scalar quantities: only state magnitude + unit
vector quantities: state magnitude, unit + direction (direction must be specific)
acceleration: generally vector, scalar if no direction
triangle of vectors: 3 vectors added, resultant = 0, polygon of vectors: >3 vectors added, resultant = 0
Vector subtraction:
1B - A = C > B + (-A) = C
2A + C = B > C = B A
[A = initial vector, B = final vector, C = change in vector]
Resolution of vectors
Vectors resolved into horizontal(Fh) and vertical(Fv) components
Fv = Fsinθ, Fh = Fcosθ
Fv and Fh of diff vectors added together as linears [up/right: +ve, down/left: -ve] > 2 final components, FV & FH > find resultant
A body acted on by 2/> forces and in equilibrium: A + B + C + = 0 > no resultant > no acc > no motion (at rest)
Back to 'A' level notes index
Back to notes index