definition of precision + what is depends on/inversely related to
precision: how close measurements are to each other (consistency of measurements)
- depends on absolute uncertainty
- inversely related to least count
absolute uncertainty (+ relative uncertainty)
uncertainty of a measurement, measure of the range of possible values around a measured value
- different from relative uncertainty, which is in relation to the measured value (expressed as a ratio or percentage)
least count + in relation to precision
minimum value that an instrument can measure
- instruments with smaller least count have more precision (makes sense because more detailed measurements)
accuracy (definition + what it depends on)
accuracy: how close measurement is to actual value
accuracy of measurement depends on the fractional uncertainty or percentage uncertainty
- accuracy is inversely related to fractional uncertainty
fractional uncertainty
indicates proportion of measured value that is uncertain
- relative measure of uncertainty or error associated with a measurement
(typically written as a ratio or percentage)
lower the percent uncertainty value, greater the accuracy
fractional uncertainty formula
least count / measured value
(for %, just multiply by 100)
which of the 3 is the most precise instrument?
- meter rod
- screw gauge
- vernier calipers
screw gauge
precision and accuracy depends on what?
precision depends on least count
accuracy depends on % uncertainty
physical quantities definition
on the basis of which laws of physics are expressed
- all those quantities that are measured accurately
base quantity vs derived quantity
base quantity (fundamental quality): are not defined in terms of other quantities (considered to be independent and cannot be derived from other quantities)
derived quantity: defined/expressed in terms of other quantities (obtained by performing math like add, subtract, divide, multiple one or more base quantities)
ex: speed = distance/time
7 base quantities
- length
- mass
- time
- electric current
- temperature
- amount of substance (# of atoms, molecules)
- luminous intensity (intensity of visible light)
list 5 examples of derived quantities
are infinite but some examples are:
velocity, acceleration, force, volume, density
2 steps in measuring a base quantity (+ ideal standard if what 2 conditions are met)
- choose a standard
- establish a procedure
(ideal standard if accessible [ruler needed so ruler present] and invariable [one min has 60 secs only])
