Introduction to SI Units and Measurement

A set of flashcards covering SI base units, derived units, nuclear physics units, scientific notation, and significant figures based on the lecture material.

Système International (SI)

The modern form of the metric system and the standard system of units most commonly used in physics, also known as the International System of Units.

Metre (m)

The SI base unit for measuring length.

Kilogram (kg)

The SI base unit for measuring mass.

Seconds (s)

The SI base unit for measuring time.

Amperes (A)

The SI base unit for measuring electrical currents.

Kelvin (K)

The SI base unit for measuring temperature.

Mole

The SI base unit used to measure the amount of substance.

Candela

The SI base unit used to measure luminous intensity.

Le Grand K

The International Prototype of the Kilogram; a platinum-iridium alloy used since 1889 as the reference to define the kilogram.

Becquerel (Bq)

The SI unit of radioactivity, defined as the activity of radioactive material in which one nucleus decays per second.

Gray (Gy)

The SI unit of ionising radiation dose, defined as one joule of radiation energy per kilogram of matter.

Sieverts (Sv)

The SI unit of ionising radiation dose that measures the health effect of radiation on living tissue (i.e. the human body).

Derived units

Units of measurement obtained by multiplication or division of the base units without the introduction of numerical factors.

Velocity

A derived unit measured in metres per second ($\text{m/s}$).

Acceleration

A derived unit measured in metres per second per second ($\text{m/s}^2$).

Energy

A derived unit measured in kilogram metres squared per second squared ($\text{kg} \times \text{m}^2/\text{s}^2$).

Conversion factor: Kilometer to Mile

$1\,km = 0.621\,\text{miles}$.

Scientific Notation Rule

The number in front of the power of ten must always be between $1$ and $10$. If 10 or greater, the power goes up; if less than 1, the power drops.

Microns

A shorthand term sometimes used to refer to micrometres.

Significant figures

Digits in a real-world number that are reliably known, representing a measure of how precisely a value is known.

Multiplication and Division Rule (Sig Figs)

The final answer should have no more significant figures than the input number with the fewest.

Addition and Subtraction Rule (Sig Figs)

The final answer should have no more decimal places than the input number with the fewest.

Zero in Significant Figures

Zeros are written to indicate precision and place value; for example, $5.000$ indicates higher precision than $5$.