The document discusses the concept of magnitudes, which are physical properties that can be measured, such as the mass or volume of an object. Magnitudes must be expressed using a number and a unit, such as 120 km/h. There is an international system that collects magnitudes and their standard units. This system identifies fundamental magnitudes as the most important ones to measure, including length, time, mass, and temperature, along with their standard units.

2. • A magnitude is a property of the material that we can
measure. For example, can we measure the mass of a
coin?. Yes, we can. So the mass of a coin is a physical
magnitude or magnitude. Can we measure the volume of
a coin?. Yes, we can. So the volume of a coin is a physical
magnitude or magnitude.
We measure the mass We measure the volume
with a scale with a test-tube
Beauty isn’t a magnitude. We can’t
measure it with an instrument or with a
machine. However, there’s a world
beauty competition every year.
Knowledge isn’t a magnitude. We can’t
measure it with an instrument or with a
machine. However, you have to pass many
exams every year.

3. We must express a magnitude with a number or quantity and a unit.
Magnitude = quantity x unit
For example, a car is running at 120 km/h. We express it like:
V = 120 km/h
Speed, (magnitude) Unit
Number or quantity
Remember : You always must express the magnitude
like a number followed by a unit.
Put the unit. Don’t forget it.
!

4. • All the magnitudes and their units are gathered in a common set
called the International System.
• Scientists choose an arbitrary number of magnitudes. They are
most important. These ones are called fundamental magnitudes.
FUNDAMENTAL MAGNITUDES AND THEIR UNITS
MAGNITUDE UNIT
Length meter (m)
Time second (s)
Mass kilogram (kg)
Temperature kelvin (K)