Physical Measurements and Errors

A set of vocabulary flashcards based on lecture notes regarding physical measurements, SI units, scientific notation, and error analysis.

Physical Quantities

Any physical property of a material or system that can be quantified and measured using numbers, consisting of a numerical value and a unit of measurement.

Unit of Measurement

A specific magnitude of a physical quantity that has been adopted by convention.

SI Units

An acronym for the French Le Systeme International d’ Unites or International System of Units, also known as the metric system.

English Units

Units also known as the Imperial System, which is primarily used by the United States.

Fundamental Units

Also called base units, these are seven building blocks that serve as the foundation for all other units and cannot be defined in terms of each other.

Derived Units

Units made by mathematically combining fundamental units, often expressed as products or ratios such as $\text{m/s}$.

Unit Prefix

Symbols placed before the symbol of a unit to specify the order of magnitude of a quantity, making it easier to express very large or very small quantities.

Scientific Notation

A mathematical expression in the form $a \times 10^n$, where $a$ is a number greater than or equal to 1 and less than 10, and $n$ is an integer.

Unit Conversion

The process of changing a measurement from one unit to another without changing its value, using conversion factors.

Conversion Factors

Values that relate one unit to another, such as $1\,\text{km} = 1000\,\text{m}$ or $1\,\text{in} = 2.54\,\text{cm}$.

Accuracy

A definition of how close a measured value is to a true or accepted value.

Precision

A term referring to how near multiple measurements are to one another.

Random Error

Errors occurring due to variations in the environment or measurement techniques, such as inconsistent reaction time when using a stopwatch.

Systematic Error

Errors caused by faulty instruments or the incorrect handling of instruments, such as a weighing scale that always reads $0.3\,\text{g}$ higher than the actual mass.

Uncertainty

A quantitative estimate of the possible range of values within which the true value of a measurement lies, due to limitations of instruments, methods, or observer skill.

Percent Uncertainty

A method of expressing reliability defined by the formula: $\text{Percent Uncertainty} = \frac{\text{Absolute Uncertainty}}{\text{Measured Value}} \times 100\%$.

Percent Error

A calculation used to determine accuracy when the correct value is known: $\text{Percent Error} = \frac{|\text{Measured Value} - \text{True Value}|}{\text{True Value}} \times 100\%$.

Significant Figures

The number of digits in a measurement that contribute to its accuracy and precision.