Complete Physics for Cambridge IGCSE®: Measurements and Units

Vocabulary flashcards based on the Measurements and Units section of the Complete Physics for Cambridge IGCSE® lecture and text.

Physical quantity

A complete measurement that is made up of two parts: a number and a unit.

Speed

The distance travelled by an object divided by the time taken, often expressed in the unit $\text{m/s}$.

Prefix

An extra symbol placed in front of a unit to make it bigger or smaller, such as kilo ($k$) for $10^{3}$ or milli ($m$) for $10^{-3}$.

Scientific notation

A method of writing numbers using powers of ten, also known as standard form.

Significant figures

The figures in a number that indicate the accuracy of a measurement.

SI units

The common system of units used in scientific work, known as Le Système International d'Unités.

Mass

A measure of the amount of substance in an object that resists changes in motion and experiences gravitational pull.

Kilogram (kg)

The SI base unit of mass.

Second (s)

The SI base unit of time, defined in terms of the frequency of an oscillation in the nucleus of a caesium atom.

Metre (m)

The SI base unit of length, defined as the distance travelled by light in a vacuum in $\frac{1}{299,792,458}$ of a second.

Micrometer

An instrument with a revolving barrel and screw thread used to make highly accurate length measurements of small objects.

Vernier calipers

An instrument fitted with an extra sliding scale used to measure internal or external lengths more accurately than a standard rule.

Zero error

An incorrect reading on an instrument when the expected reading is zero, requiring a correction to the final measurement.

Period

The time taken for a pendulum to make one complete swing.

Volume

The quantity of space an object takes up, with the SI unit being the cubic metre ($\text{m}^{3}$).

Density

The ratio of mass to volume for a material, calculated using the formula $\rho = \frac{m}{V}$.

Displacement can

A container used to measure the volume of an irregular solid by collecting the water the object displaces when lowered into it.

Hydrometer

A small float used to quickly determine the density of a liquid by how high it sits in that liquid.

Weight

The downward pull of gravity on an object, recorded as a force in units called newtons (N).

Inertia

The resistance of an object to a change in its velocity, which increases with the mass of the object.