Physics & Physical Measurement Revision
Order of Magnitude
* 100.5 = 3.16 (rounding value) * e.g. 4,200,000=4.2*106 * since 4.2 > 3.16 the magnitude is 107 (6 is rounded up)
The SI System of Fundamental and Derived Units
* Fundamental SI Units:
Quantity | SI Unit | SI Symbol | length | meter | m | mass | kilogram | kg | time | second | s | electric current | ampere | A | thermodynamic temperature | Kelvin | K | amount of substance | mole | m | luminous intensity | candela | cd |
* Derived SI Units
Quantity | SI Unit | SI Symbol | Fundamental SI Units involved | frequency | hertz | Hz | s-1 | force | Newton | N | kg*m*s-2 | work/energy | joule | J | kg*m2*s-2 | power | watt | W | kg*m2*s-3 | pressure | Pascal | Pa | kg*m-1*s-2 | charge | coulomb | C | A*s | potential difference | volt | V | kg*m2*s-3*A-1 | resistance | ohm | Ω | kg*m2*s-3*A-2 |
Systematic and Random Errors
* Systematic error * Affects each measurement the same way * Error by system * E.g. lack of calibration (zero error) * E.g. Wrong theory or equation * Not accurate * Random error * Different for each measurement * By human error or environmental influence * E.g. temperature variation * E.g. Not enough data collected * Not precise
* Accuracy – how close the results are from the true value * Indicated by relative or percentage error * Precision – how the different results vary from each other * Indicated by absolute error
* Reduce random error * Consistent experimental procedure * Choose instrument with higher degree of accuracy * Reduce variation (air current, temperature variation, vibration…) * Systematic error corrected before the experiment
Significant Figures
* Used to indicate degree of accuracy of precision in a measurement * Rules for significant figures: * All non-zero digits are significant *
* 100.5 = 3.16 (rounding value) * e.g. 4,200,000=4.2*106 * since 4.2 > 3.16 the magnitude is 107 (6 is rounded up)
The SI System of Fundamental and Derived Units
* Fundamental SI Units:
Quantity | SI Unit | SI Symbol | length | meter | m | mass | kilogram | kg | time | second | s | electric current | ampere | A | thermodynamic temperature | Kelvin | K | amount of substance | mole | m | luminous intensity | candela | cd |
* Derived SI Units
Quantity | SI Unit | SI Symbol | Fundamental SI Units involved | frequency | hertz | Hz | s-1 | force | Newton | N | kg*m*s-2 | work/energy | joule | J | kg*m2*s-2 | power | watt | W | kg*m2*s-3 | pressure | Pascal | Pa | kg*m-1*s-2 | charge | coulomb | C | A*s | potential difference | volt | V | kg*m2*s-3*A-1 | resistance | ohm | Ω | kg*m2*s-3*A-2 |
Systematic and Random Errors
* Systematic error * Affects each measurement the same way * Error by system * E.g. lack of calibration (zero error) * E.g. Wrong theory or equation * Not accurate * Random error * Different for each measurement * By human error or environmental influence * E.g. temperature variation * E.g. Not enough data collected * Not precise
* Accuracy – how close the results are from the true value * Indicated by relative or percentage error * Precision – how the different results vary from each other * Indicated by absolute error
* Reduce random error * Consistent experimental procedure * Choose instrument with higher degree of accuracy * Reduce variation (air current, temperature variation, vibration…) * Systematic error corrected before the experiment
Significant Figures
* Used to indicate degree of accuracy of precision in a measurement * Rules for significant figures: * All non-zero digits are significant *