1. Units, Dimensions 4Measwuments
Physical Guantity The
The quantity which can be measu recd
and by means o which we diseribe the Lc s Pysies
Called physical quantities.
e. mam, Jength, time, dinsity , vloc:ty etc.
On the other harol vaious happenings in ite eg»
appine s s , S o r o w etc. a L not physical quantity s
hese Can not be measuaAd.
Classification -
(1 Bazed on their dlirectionad propehies -
(L) Scalans -
The physical quantity which have only magnitude
Dur no direction caluol Scala quantities.
etc.
e3
eg mam, ungth, density
CCi) Vectovs-
The phusical uantity which have both magni-
tad and dinschion ane callud vectoY quantities.
Force, dusplacement, velocity etc.
e8
Note-There ahe Some physica quantites whieh are
not
and
Completely specified
diniction. These
ewen
phyaical
bby magnitudu, unit
quantities are Callad
tensoYS
e mome nt o inentia, Stre ss, pevmittivity. ec.
,(2) Based on thlr dependluncy
(i Funolamental or Babe quartities -
The
phsical quanti ties which are indupenderrt
each other and alu other quantities a u Callud funda-
o
mentaM oY base quantities.
ee 8 ength, m a , ime etc.
(ii) Deived Guantities-
An physicaN quanit which
Any be deríved
Can
from the fundamental physical quantities by mutiplying
b
OY
dividing them is calld
dividing deived physical quantit
e.8
e 3 sPeed, olenaity, accelkration etc.
Units Unit is a standarol quantity with which a
phpaical quantity oh same Kind is Compaked for measuring
Pitical
Phyaical uartit Magnitudle x Unit
nxu
here , n represents the numerical valuL and u repreerts
the unit.
Thus while expressing dejinite amount o phyaical
quontity, as the unit (u changes, the magnitudi (n)
will also change but product n u ' will Yemain same.
e. nu = Constan or n
naua Conatantt
Hence m a t, it shows that smallr the unit oh
phsical quanti Larger will be the magnitude and
vice-versa.
,System o Units
CGS Sstem
In this Aystem the fundlamental 9uantities
an ungth, mas and ime and thur respecive units
a n centimeter Cm.), ram ( 3:) and second (S .
2 FPS Syatem.
In this sytem ngth, mas and time
an taKen as fundamental quantitis and their units
a e foot (ft), pound (Lb) and second (s) respectively-
MKS System
In this Sstemn aso h fundamental
quanti ties ane Lengh mass and time but h i r funola
mentau units are meter (m), kilogran (Kg) and secomd
s ) respecively
4 SI Units.
TRAs sstem is moditication over he
MKS syotem and so also Knouon as Radionalised
MKS System. In SI syatem there o e seven funclamental
units and two supplementary units.
Funclamental Units amd spmbel
SN CuGndit Unit Smbo51
Mas
Kilgram
2.
Length Meter
3. Time Second S
4. Temperadure Kelvin K
S. Luminuous Intensity Candela Cod
6. Eleetrie Current Ampere A
7. Qunity o Matter Mole mol
, Besides the above seven fundamenta units t o
Supplumentay units ahe also duinucl-
Radian or plane angle and stermdian fov soid angie.
Some dejinitions of fundamantal units in SI sstem
4) Metre
One metre s the distana which accommodates
16 50,76373 waves in va cuum of ovange red g h emitteed
by Ky86
(a) Kilogram
1 Kilugam is the mas oh platinum iridium
Cyunele r of ouamefer equal to t s huight which is preserve
in a vatzlt at international Bureau ofweighds and measures
at Severs nea Pais.
1 Kilogramis the mass ob 1 t . of water at 4'c.
(3.) Second
One second is that amount o ime in which
a Cesium -33 atom makes 9192,631,770 vibrations in a
Ceum watch
(4.) Ampeie
OnL ampere is that electric Cunen which
whun pased through tuo pmalll Conduetors ob infinte
section placeel at unit distana
ngth md u negigible cross
apat produe a force oj 2x 16 N/m.
(5.) Candla
T the uminow intensity in a direction
a rign angles to the S j a e o a black body at a
empeature equad to melhing point o platinum Linder
Presure of 101,325 N/m
Physical Guantity The
The quantity which can be measu recd
and by means o which we diseribe the Lc s Pysies
Called physical quantities.
e. mam, Jength, time, dinsity , vloc:ty etc.
On the other harol vaious happenings in ite eg»
appine s s , S o r o w etc. a L not physical quantity s
hese Can not be measuaAd.
Classification -
(1 Bazed on their dlirectionad propehies -
(L) Scalans -
The physical quantity which have only magnitude
Dur no direction caluol Scala quantities.
etc.
e3
eg mam, ungth, density
CCi) Vectovs-
The phusical uantity which have both magni-
tad and dinschion ane callud vectoY quantities.
Force, dusplacement, velocity etc.
e8
Note-There ahe Some physica quantites whieh are
not
and
Completely specified
diniction. These
ewen
phyaical
bby magnitudu, unit
quantities are Callad
tensoYS
e mome nt o inentia, Stre ss, pevmittivity. ec.
,(2) Based on thlr dependluncy
(i Funolamental or Babe quartities -
The
phsical quanti ties which are indupenderrt
each other and alu other quantities a u Callud funda-
o
mentaM oY base quantities.
ee 8 ength, m a , ime etc.
(ii) Deived Guantities-
An physicaN quanit which
Any be deríved
Can
from the fundamental physical quantities by mutiplying
b
OY
dividing them is calld
dividing deived physical quantit
e.8
e 3 sPeed, olenaity, accelkration etc.
Units Unit is a standarol quantity with which a
phpaical quantity oh same Kind is Compaked for measuring
Pitical
Phyaical uartit Magnitudle x Unit
nxu
here , n represents the numerical valuL and u repreerts
the unit.
Thus while expressing dejinite amount o phyaical
quontity, as the unit (u changes, the magnitudi (n)
will also change but product n u ' will Yemain same.
e. nu = Constan or n
naua Conatantt
Hence m a t, it shows that smallr the unit oh
phsical quanti Larger will be the magnitude and
vice-versa.
,System o Units
CGS Sstem
In this Aystem the fundlamental 9uantities
an ungth, mas and ime and thur respecive units
a n centimeter Cm.), ram ( 3:) and second (S .
2 FPS Syatem.
In this sytem ngth, mas and time
an taKen as fundamental quantitis and their units
a e foot (ft), pound (Lb) and second (s) respectively-
MKS System
In this Sstemn aso h fundamental
quanti ties ane Lengh mass and time but h i r funola
mentau units are meter (m), kilogran (Kg) and secomd
s ) respecively
4 SI Units.
TRAs sstem is moditication over he
MKS syotem and so also Knouon as Radionalised
MKS System. In SI syatem there o e seven funclamental
units and two supplementary units.
Funclamental Units amd spmbel
SN CuGndit Unit Smbo51
Mas
Kilgram
2.
Length Meter
3. Time Second S
4. Temperadure Kelvin K
S. Luminuous Intensity Candela Cod
6. Eleetrie Current Ampere A
7. Qunity o Matter Mole mol
, Besides the above seven fundamenta units t o
Supplumentay units ahe also duinucl-
Radian or plane angle and stermdian fov soid angie.
Some dejinitions of fundamantal units in SI sstem
4) Metre
One metre s the distana which accommodates
16 50,76373 waves in va cuum of ovange red g h emitteed
by Ky86
(a) Kilogram
1 Kilugam is the mas oh platinum iridium
Cyunele r of ouamefer equal to t s huight which is preserve
in a vatzlt at international Bureau ofweighds and measures
at Severs nea Pais.
1 Kilogramis the mass ob 1 t . of water at 4'c.
(3.) Second
One second is that amount o ime in which
a Cesium -33 atom makes 9192,631,770 vibrations in a
Ceum watch
(4.) Ampeie
OnL ampere is that electric Cunen which
whun pased through tuo pmalll Conduetors ob infinte
section placeel at unit distana
ngth md u negigible cross
apat produe a force oj 2x 16 N/m.
(5.) Candla
T the uminow intensity in a direction
a rign angles to the S j a e o a black body at a
empeature equad to melhing point o platinum Linder
Presure of 101,325 N/m
