Measurements and Uncertainty Flashcards
SI units
Length (m) Time (s) Temp (*C) Luminicity Intencity (cd) Mass (kg) Current (A) Amount of substance (mol)
Prefixes for power of tens
Peta, tera, giga, mega, kilo
Milli, micro, nano, pico,femto
× to get smaller unit, / to get bigger unit
Sig fig for addition or mean
To least amount of decimal places
Sig fig for multiplication and division
Use least number of sig figs
Measurement error
Difference between true value and measured value
Uncertainty
Interval between which true value lies
Reading and uncertainty
Only 1 value being taken
+ or - half the resolution
Measurements and uncertainty
2 readings to account for zero point
(E.g. change in mass)
Used sets zero point rather than manufacturer
So less accurate
+ or - resolution
Repeated measurements and uncertainty
Taking many sets of data and finding mean
+ or - half the range
Percentage uncertainty
Absolute uncertainty/mean value *100
Adding and subtracting mesurements (uncertainty)
Add ABSOLUTE UNCERTAINTY of variables
Multiplying and dividing mesurements (uncertainty)
Add PERCENTAGE UNCEETAINTY of variables
Squaring or curbing mesurements (uncertainty)
a=b(^c)
%uncertainty of a= c × %uncertainty of b
Random error
- due to problem in resolution or quality of technique
- cant be eliminated but can be minimised by repeated results and taking out anomalies
- data not close to line of best fit
Stsyamatic errors
- zero error/faulty calibration
- inabality to mesure end of object at same reference point (e.g. center of mass in pendulam)
- resistance in connecting wires
- friction and air resistance
- all points close to line of best fit but doesn’t go through origin or has incorrect gradient
