## IB Physics Glossary

All categories |

## TOPIC 1: MEASUREMENTS AND UNCERTAINTIES |
---|

## Accuracytells us how close the measured value of a quantity is to its true value. An accurate measurement is "close" to a true value. An inaccurate measurement is "far" from a true value. | |

## Derived units are not fundamental but can be expressed in terms of fundamental units. | |

## Fundamental units are the most basic units which cannot be expressed in terms of other units. The seven fundamental units are 1. meter (m); 2. second (s); 3. kilogram (kg); 4. Kelvin (K); 5. The Ampere (A); 6. mole (mol); 7. candela (cd). | |

## Precision tells us how consistent repeated measurements are. A precise set of measurements are relatively closer together. An imprecise set of measurements are spread apart. | |

## Proportional relationship or , occurs when the relationship between and is linear with a zero y-intercept value, that is, a straight line passing through the origin. The x- and y-error bars may allow a range of values for the y-intercept, because the lines of max & min gradients, thus showing a possible proportional relationship for a best-fit straight line even if its y-intercept value is non-zero. Beware, for the IB, a best-fit line can be any curve which fits the data points. It does not mean the best-fit straight line. | |

## Random error is a fluctuating error often present in experiments. It is linked to precision: imprecise data => "high" random error; precise data => "low" random error. Repeated measurements do reduce random errors. Sources of random errors can include varying reading/human error and other randomly flucuating factors which cannot be controlled during experiments. | |

## Scalar multiplication | |

## Scalar quantities have magnitude only. Direction or changes in direction have no effect on scalar quantities. Examples include distance, speed, mass and temperature. | |

## Signifiant figuresa rule, the number of significant digits in a result should not exceed that of the least precise value upon which it depends. | |