Measurements, Units, and Errors in Physics

A set of vocabulary flashcards covering key concepts of physical measurements, SI units, scientific notation, unit conversions, significant figures, and measurement uncertainties.

Measurement

The art of comparing unknown values to a standard for a particular quantity.

Units

The standards in which physical quantities are expressed.

Fundamental Units

The base units for fundamental physical quantities, which are meter, kilogram, second, kelvin, ampere, candela, and mole.

SI Base Units

The seven standard units of measurement defined in the International System of Units: second ($s$) for time, meter ($m$) for length, kilogram ($kg$) for mass, ampere ($A$) for electric current, kelvin ($K$) for thermodynamic temperature, mole ($mol$) for amount of substance, and candela ($cd$) for luminous intensity.

Conversion of Units

The conversion between different units of measurement for the same quantity, typically carried out through multiplicative conversion factors.

Scientific Notation

An exponential notation method written in the standard format $N \times 10^e$, where $N$ represents a single nonzero digit to the left of the decimal point and $e$ represents the exponent.

Significant Figures

The digits in a measured number that are known with certainty plus the last digit that is uncertain.

Atlantic-Pacific Rule

A shorthand rule for counting significant figures: if a decimal point is present, start counting from the left (Pacific side) at the first nonzero digit; if a decimal point is absent, start counting from the right (Atlantic side) at the first nonzero digit.

Accuracy

The degree of closeness between a measured value and the theoretical or accepted true value.

Precision

The degree of agreement or consistency obtained when repeating measurements of the same object.

Accuracy vs. Precision (Target Diagram)

A visual representation where hitting the center target represents high accuracy and grouping thrown darts tightly together represents high precision.

Systematic Error

An error that occurs when measurements are reproducible (precise) but inaccurate, typically associated with specific causes that can be determined and corrected.

Ancient Methods of Measuring Length

Historical body-based units used for measuring length, including hand span, fathom, cubit, and foot.

Instruments for Measuring Volume

Laboratory apparatuses used to measure liquid volume, including the graduated cylinder, syringe, buret, pipet, and volumetric flask.