Physics Units and Measurements Quiz

Units and Measurements

• Physics relies on precise measurements of physical quantities for accurate results.
• Measurement involves comparing an unknown quantity to a known standard quantity.
• Accurate measurement is crucial for technological development.
• The accuracy of measurement depends on the method and instrument used.

Units of Physical Quantity

• A unit defines the standard for measuring a physical quantity.
• Example: "3 meters" indicates the length, where 3 is the magnitude and meter is the unit.
• Requirements for a standard unit:
  • Universally accepted and recognized.
  • Clearly defined and specific.
  • Consistent over time and location.
  • Easily reproducible and durable.
  • Comparable with similar units.
  • Adequate size for everyday measurements.
  • Readily obtainable.

Physical Quantities

• A physical quantity is measurable and can be quantified.
• Examples include length, mass, time, current, force, work, and power.

Fundamental and Derived Quantities

• Fundamental Quantities:

  • Basic quantities that do not depend on other quantities for measurement.
  • Seven fundamental quantities:
    • Length (metre, m)
    • Mass (kilogram, kg)
    • Time (second, s)
    • Temperature (kelvin, K)
    • Electric current (ampere, A)
    • Luminous intensity (candela, cd)
    • Amount of substance (mole, mol)

• Supplementary Quantities:

  • Plane angle (radian, rad)
  • Solid angle (steradian, sr)

• Derived Quantities:

  • Depend on one or more fundamental quantities for their measurement.
  • Examples include:
    • Density: kg/m³ (derived from mass and volume)
    • Area: m²
    • Volume: m³
    • Velocity: m/s
    • Acceleration: m/s²
    • Force: newton (N)
    • Pressure: N/m²
    • Speed: m/s
    • Work: joule (J)

Units Summary

• Fundamental units are the basis for all measurements and remain constant.
• Derived units are formulated from fundamental units and describe related physical concepts.