How Do We Use Measurements SI UNITS
5 Minutes
Measurement and SI units for kids: learn why we need units, how FPS and MKS systems worked, and the seven base SI units. A short science lesson in English.
- Instruments, standard quantities, and why units are needed to measure
- Measuring systems like FPS, CGS, and MKS used around the world
- The 1960 France conference and a memory game on the 7 base SI units
What this lesson teaches
Measurement is the process of comparing the size or amount of an unknown object with a known standard object. It allows people to determine exact physical quantities in daily life instead of guessing without clear values.
Three essentials of measurement
- An instrument is the tool used to measure something, such as a meter scale for a table, a weighing machine for vegetables and fruits, a thermometer for fever, or a clock for time.
- A standard quantity is a measurable physical quantity that is agreed upon and used as a common base to find an unknown quantity.
- A unit is the accepted term used to describe the measurement of a standard object, allowing people to state exact amounts such as two meters of rope or one kilogram of rice.
Early unit systems
Different countries originally used their own systems named after the first letters of their measurement units. These included the FPS, CGS, and MKS systems, which measured length in feet, centimeters, or meters, and mass in pounds, grams, or kilograms. All three systems used the second to measure time. Having different systems caused trade confusion, such as a buyer requesting kilograms of apples in a place that only used pounds.
Creation of SI units
To avoid confusion and trade disputes between countries, scientists from around the world gathered for a general conference in France in 1960. They declared a single worldwide standard called the International System of Units, abbreviated as SI units. This agreement established seven standard basic units that everyone across the world uses to measure physical quantities.
The seven basic SI units
- Length has the base unit of meter, and mass has the base unit of kilogram.
- Time has the base unit of second, and temperature has the base unit of kelvin.
- Electric current has the base unit of ampere.
- Amount of substance has the base unit of mole, and luminous intensity has the base unit of candela.