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units physical quantities . and vectors
Fundamental physical quantities
Mass (Kg ) :
past definition : 1 kg =
mass of one dm ' water at 4 degrees
current definition : 1kg =
mass of a piece of Pt lr
-
alloy in Paris ( since 1901 )
time ( s )
past definition : a certain part of the mean solar day
current definition : 1s =
duration of 9192632770 periods of the radiation corresponding to the transition
between two hyperfine levees of the ground state Ce 133
length (m ) :
past definition : length of a certain bar in Paris
current definition : 1m =
distance light travels in vacuum in 11299792458 s
uncertainty & significant figures
ma
"
absolute uncertainty : when there are multiple trials /measurements
reading uncertainty :
based on the measuring instrument
absolute uncertainties (A) have a unit
Abs . Unc .
relative uncertainty measurement :
relative uncertainty comes in the form of fractional relative uncertainties and percentage
relative uncertainties .
significant figures the amount of digits ( I 9) as well as leading zeros after a decimal point and
-
:
ending zeros
mathematical operations :
multiplication and division :
significant figures : not more significant figures than the fewest significant figures
uncertainty : add relative uncertainties
addition and subtraction :
significant figures fewest digits to : the right of the decimal point .
uncertainty : add absolute uncertainty
scalar and vector quantities
scalar :
single number with a unit ( no direction) vector : magnitude and direction
examples :
examples :
1. Temperature i. displacement
2. Time 2 . Velocity
3. mass 3 .
acceleration
4. Volume 4 .
force
5. speed 5 . electric field
6. density a. magnetic field
units physical quantities . and vectors
Fundamental physical quantities
Mass (Kg ) :
past definition : 1 kg =
mass of one dm ' water at 4 degrees
current definition : 1kg =
mass of a piece of Pt lr
-
alloy in Paris ( since 1901 )
time ( s )
past definition : a certain part of the mean solar day
current definition : 1s =
duration of 9192632770 periods of the radiation corresponding to the transition
between two hyperfine levees of the ground state Ce 133
length (m ) :
past definition : length of a certain bar in Paris
current definition : 1m =
distance light travels in vacuum in 11299792458 s
uncertainty & significant figures
ma
"
absolute uncertainty : when there are multiple trials /measurements
reading uncertainty :
based on the measuring instrument
absolute uncertainties (A) have a unit
Abs . Unc .
relative uncertainty measurement :
relative uncertainty comes in the form of fractional relative uncertainties and percentage
relative uncertainties .
significant figures the amount of digits ( I 9) as well as leading zeros after a decimal point and
-
:
ending zeros
mathematical operations :
multiplication and division :
significant figures : not more significant figures than the fewest significant figures
uncertainty : add relative uncertainties
addition and subtraction :
significant figures fewest digits to : the right of the decimal point .
uncertainty : add absolute uncertainty
scalar and vector quantities
scalar :
single number with a unit ( no direction) vector : magnitude and direction
examples :
examples :
1. Temperature i. displacement
2. Time 2 . Velocity
3. mass 3 .
acceleration
4. Volume 4 .
force
5. speed 5 . electric field
6. density a. magnetic field
