Overview
This lecture introduces the seven base SI (International System of Units) units and demonstrates how they combine to form derived units commonly used in physics.
Base SI Units
- The unit for length is the meter (m).
- The unit for mass is the kilogram (kg).
- The unit for time is the second (s).
- The unit for temperature is the Kelvin (K).
- The unit for amount of substance is the mole (mol).
- The unit for electric current is the ampere (A).
- The unit for luminous intensity is the candela (cd).
Derived SI Units
- Units can be combined to form other units, called derived units.
- Speed/velocity is measured in meters per second (m/s).
- Volume is measured in cubic meters (m³).
- Density is measured in kilograms per cubic meter (kg/m³).
- Force (Newton) is measured in kilogram meters per second squared (kg·m/s²).
- Most physics units are combinations of base SI units, especially length, mass, and time.
Key Terms & Definitions
- Meter (m) — SI unit of length.
- Kilogram (kg) — SI unit of mass.
- Second (s) — SI unit of time.
- Kelvin (K) — SI unit of temperature.
- Mole (mol) — SI unit for amount of substance.
- Ampere (A) — SI unit of electric current.
- Candela (cd) — SI unit of luminous intensity.
- Derived Units — Units formed by combining base SI units (e.g., m/s, kg/m³).
Action Items / Next Steps
- Memorize the seven base SI units and their abbreviations.
- Practice converting common physical quantities to SI units.