# Physics in addition to Physical Measurement The S.I. System St in addition to ards of Measurement Fundamental Quantities The 7 Fundamentals

## Physics in addition to Physical Measurement The S.I. System St in addition to ards of Measurement Fundamental Quantities The 7 Fundamentals

Mintz, Howard, Federal, Civil Courts Reporter has reference to this Academic Journal, PHwiki organized this Journal Physics in addition to Physical Measurement Topic 1.2 Measurement in addition to Uncertainties The S.I. System St in addition to ards of Measurement SI units are those of the Système International dUnités adopted in 1960 Used as long as general measurement in most countries worldwide

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Fundamental Quantities Some quantities cannot be measured in a simpler as long as m in addition to as long as convenience they have been selected as the basic quanitities They are termed Fundamental Quantities, Units in addition to Symbols The 7 Fundamentals Length metre m Mass kilogram kg Time second s Electric current ampere A Thermodynamic temp Kelvin K Luminous Intensity c in addition to ela cd Amount of a substance mole mol Derived Quantities When a quantity involves the measurement of 2 or more fundamental quantities it is called a Derived Quantity The units of these are called Derived Units

Derived Units Examples Acceleration ms-2 Momentum kgms-1 or Ns Some derived units have been given their own specific names in addition to symbols Force N = kg ms-2 Joule J = kgm2s-2 St in addition to ards of Measurement Scientists in addition to engineers need to make accurate measurements so that they can exchange in as long as mation To be useful a st in addition to ard of measurement must be Invariant, Accessible in addition to Reproducible 3 St in addition to ards (FYI  not tested) The Meter :- the distance traveled by a beam of light in a vacuum over a defined time interval ( 1/299 792 458 seconds) The Kilogram :- a particular platinum-iridium cylinder kept in Sevres, France The Second :- the time interval between the vibrations in the caesium atom (1 sec = time as long as 9 192 631 770 vibrations)

Conversions You will need to be able to convert from one unit to another as long as the same quanitity J to kWh (energy) J to eV (energy) Years to seconds (time) And between other systems in addition to SI Note: you should be able to do basic conversions now in addition to others will be developed throughout the year SI Format The accepted SI as long as mat is ms-1 not m/s ms-2 not m/s/s The IB will recognize work reported with /, but will only use the SI as long as mat when providing info. Uncertainity in addition to error in measurement

Errors Errors can be divided into 2 main classes R in addition to om errors Systematic errors Mistakes Mistakes on the part of an individual such as misreading scales poor arithmetic in addition to computational skills wrongly transferring raw data to the final report using the wrong theory in addition to equations These are a source of error but are not considered as an experimental error Systematic Errors Cause a r in addition to om set of measurements to be affected in the same way It is a system or instrument issue

Systematic Errors result from Badly made instruments Poorly calibrated instruments An instrument having a zero error, a as long as m of calibration Poorly timed actions Instrument parallax error Note that systematic errors are not reduced by multiple readings R in addition to om Errors Are due to unpredictable variations in per as long as mance of the instrument in addition to the operator R in addition to om Errors result from Vibrations in addition to air convection Misreading Variation in thickness of surface being measured Using less sensitive instrument when a more sensitive instrument is available Human parallax error

Reducing R in addition to om Errors R in addition to om errors can be reduced by taking multiple readings, in addition to eliminating obviously erroneous result or by averaging the range of results. Accuracy Accuracy is an indication of how close a measurement is to the accepted value indicated by the relative or percentage error in the measurement An accurate experiment has a low systematic error Precision Precision is an indication of the agreement among a number of measurements made in the same way indicated by the absolute error A precise experiment has a low r in addition to om error

Reducing the Effects of R in addition to om Uncertainties Take multiple readings When a series of readings are taken as long as a measurement, then the arithmetic mean of the reading is taken as the most probable answer The greatest deviation from the mean is taken as the absolute error Absolute/fractional errors in addition to percentage errors We use ± to show an error in a measurement (208 ± 1) mm is a fairly accurate measurement (2 ± 1) mm is highly inaccurate Absolute, fractional, in addition to relative uncertainty Assume we measure something to be 208 ± 1 mm in length 1 mm is the absolute uncertainty 1/208 is the fractional uncertainty (0.0048) 0.48 % is the relative (percent) uncertainty

Combining uncertainties To determine the uncertainty of a calculated value For addition in addition to subtraction, add absolute uncertainities For multiplication in addition to division add percentage uncertainities When using exponents, multiply the percentage uncertainty by the exponent Combining uncertainties If one uncertainty is much larger than others, the approximate uncertainty in the calculated result may be taken as due to that quantity alone Significant Figures The number of significant figures should reflect the precision of the values used as input data in a calculation Simple rule: For multiplication in addition to division, the number of significant figures in a result should not exceed that of the least precise value upon which it depends

Uncertainties in graphs Graphical Techniques Graphing is one of the most valuable tools in data analysis because it gives a visual display of the relationship between two or more variables shows which data points do not obey the relationship gives an indication at which point a relationship ceases to be true used to determine the constants in an equation relating two variables You need to be able to give a qualitative physical interpretation of a particular graph

St in addition to ard Graphs – hyperbola A hyperbola shows that y is inversely proportional to x i.e. y 1/x or y = k/x where k is the constant of proportionality St in addition to ard Graphs – hyperbola again An inverse square law graph is also a hyperbola i.e. y 1/x2 or y = k/x2 where k is the constant of proportionality

## Mintz, Howard Federal, Civil Courts Reporter

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