In physics, we measure physical quantities like length, mass, and time using different systems of units. A system of units is a set of standard measurements used to compare quantities consistently.

The CGS System (Centimeter-Gram-Second)

The CGS system is based on small units. It defines length in centimeters (cm), mass in grams (g), and time in seconds (s). Scientists often use this system for small-scale experiments in laboratories. For example, if you measure the width of a small paper clip, you use centimeters. The gram is the unit for mass, which is one-thousandth of a kilogram.

The FPS System (Foot-Pound-Second)

The FPS system is known as the British Engineering System. It measures length in feet (ft), mass in pounds (lb), and time in seconds (s). You might see this system in everyday life, especially in countries like the United States. For instance, architects measure the height of a room in feet, and people often measure their body weight in pounds. This system is not commonly used in scientific research because it is difficult to convert units compared to the metric system.

The MKS System (Meter-Kilogram-Second)

The MKS system is the foundation for the modern International System of Units (SI). It uses larger base units: meters (m) for length, kilograms (kg) for mass, and seconds (s) for time. Because these units are convenient for large-scale engineering and everyday measurements, most of the world uses this system. When you measure the distance between two cities, you use kilometers, which are multiples of the meter. When you buy groceries, you use kilograms to measure the mass of vegetables.

Comparison of Systems

• CGS: Uses smaller units; common in physics lab research.
• FPS: Uses feet and pounds; common in daily life in specific countries.
• MKS: Uses meters and kilograms; the global standard for science and engineering.

Each system relies on the 'Second' as the universal unit of time, showing that time is a constant factor across all scientific measurements.