General Physics Chapter 1

Derived Quantities

Defined in terms of the seven base quantities via a system of quantity equations. The SI derived units for these derived quantities are obtained from these equations and the seven SI base units.

Base Quantity

Must be defined in terms of a standard. Ex: meter, second, kilogram, ampere, kelvin, mole, candela.

Accuracy

refers to how close a measurement is to the true value. Ex: if a ruler was manufactured with a 2% error, the accuracy of its measurement of the board's width (about 8.8cm) would be about 2% of 8.8cm or about +/-0.2cm.

Precision

refers to the repeatability of the measurement using a given instrument. Ex: if you measure the width of a board many times, getting results like 8.81cm, 8.85cm, 8.78cm, 8.82cm, you could say the measurements give a percision a bit better than 0.1cm.