Measurements and Uncertainty Flashcards

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1
Q

SI units

A
Length (m)
Time (s)
Temp (*C)
Luminicity Intencity (cd)
Mass (kg)
Current (A)
Amount of substance (mol)
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2
Q

Prefixes for power of tens

A

Peta, tera, giga, mega, kilo
Milli, micro, nano, pico,femto

× to get smaller unit, / to get bigger unit

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3
Q

Sig fig for addition or mean

A

To least amount of decimal places

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4
Q

Sig fig for multiplication and division

A

Use least number of sig figs

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5
Q

Measurement error

A

Difference between true value and measured value

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6
Q

Uncertainty

A

Interval between which true value lies

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7
Q

Reading and uncertainty

A

Only 1 value being taken

+ or - half the resolution

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8
Q

Measurements and uncertainty

A

2 readings to account for zero point
(E.g. change in mass)
Used sets zero point rather than manufacturer
So less accurate

+ or - resolution

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9
Q

Repeated measurements and uncertainty

A

Taking many sets of data and finding mean

+ or - half the range

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10
Q

Percentage uncertainty

A

Absolute uncertainty/mean value *100

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11
Q

Adding and subtracting mesurements (uncertainty)

A

Add ABSOLUTE UNCERTAINTY of variables

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12
Q

Multiplying and dividing mesurements (uncertainty)

A

Add PERCENTAGE UNCEETAINTY of variables

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13
Q

Squaring or curbing mesurements (uncertainty)

A

a=b(^c)

%uncertainty of a= c × %uncertainty of b

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14
Q

Random error

A
  • 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
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15
Q

Stsyamatic errors

A
  • 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
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16
Q

assesing reliability

A
  • how strong is colleration
  • go through origin when predicted
  • disregarded anomolous results
  • %uncertainty less then 10
  • final value within range of original readings
17
Q

uncertainties and errors shown on graphs

A
  • uncertainty shown as error bar
  • 2 lines of worst fit plotted and find their gradient (m1,m2)
  • percent uncertainty of gradient is (m1-m2)/m*100