measurements and their errors

prefixes

T - 12

G - 9

M - 6

k - 3

c - -2

m - -3

n - -6

p - -9

7 base units

Mass -kg

Temp - degrees c

Time - s

Current - A

amount - mol

length - m

light intensity- candela (cd)

SI base unit for joule

Kgm2s2

Newton base unit

Kgm/s2

Coulomb base unit

As

Volt base unit

(Kgm2s2)/As

What is a reading

A single judgement

Eg balance, voltmeter

What is a measurement?

a judgement of two values

Eg. Ruler/ stopwatch

Uncertainty for a reading formula

+or- half the smallest division

Uncertainty for a measurement formula

Two judgements +or- smallest division

What is the smallest division

The resolution

Eg. 0.1 cm on a cm ruler or

0.01 second on a stopwatch

Factor in human reaction time

0.2 seconds

Accuracy

Result is close to the true value

Precision

Multiple readings are numerically close together

Random error

• Fluctuate about a mean

  eg:

• Reading uncertainties

• Environmental factors

Systematic error

• consistent difference between measured value and true value

Eg

Calibration error

Zero error

Parallax error

Percentage uncertainty formula

(absolute uncertainty/ value) x 100