Study Notes on Physical Quantities and Measurement

Observations and Basic Questions in Physics

  • Physicists conduct observations and seek basic answers through measurement.

  • Fundamental questions include:

    • How big is an object?

    • How much mass does it have?

    • How far did it travel?

  • Various instruments are used for measurements such as:

    • Meter stick

    • Balance

    • Stopwatch

  • Measurements of physical quantities are expressed in standardized units to provide meaningful comparisons.

Standardized Units and the International System (SI)

  • Physical quantities can be represented in various units including:

    • Meters for length (e.g. in races)

    • Kilometers for long distances

  • The importance of standardized units:

    • Ensures clarity and comparability of measurements.

    • Avoids confusion – distances in unexplained units are unhelpful.

  • The SI system includes seven fundamental physical units:

    1. Length - Meter (m)

    2. Mass - Kilogram (kg)

    3. Time - Second (s)

    4. Electric Current - Ampere (A)

    5. Temperature - Kelvin (K)

    6. Amount of Substance - Mole (mol)

    7. Luminous Intensity - Candela (cd)

  • SI units are widely acknowledged and used in the scientific community reflecting a global preference over English (imperial) units, which are primarily used by the United States and some other nations.