Physics Basics: Units and Measurements

Fundamental Units

• There are seven fundamental units in physics:
  1. Meter (m) - length
  2. Kilogram (kg) - mass
  3. Second (s) - time
  4. Ampere (A) - electric current
  5. Kelvin (K) - thermodynamic temperature
  6. Mole (mol) - amount of substance
  7. Candela (cd) - luminous intensity

Derived Units

• Derived units are formed by combining fundamental units:
  • Velocity: m/s
  • Acceleration: m/s²
  • Force: N (Newton) = kg·m/s²
  • Energy: J (Joule) = N·m = kg·m²/s²
  • Power: W (Watt) = J/s = kg·m²/s³

Prefixes

• Prefixes are used to denote multiples and fractions of units:
  • kilo- (k): 10³
  • centi- (c): 10⁻²
  • milli- (m): 10⁻³
  • micro- (μ): 10⁻⁶
  • nano- (n): 10⁻⁹
  • pico- (p): 10⁻¹²

Measurement Uncertainty

• Measurement uncertainty arises due to limitations in measurement tools and techniques:
  • Absolute uncertainty: the maximum possible error in a measurement
  • Relative uncertainty: the ratio of absolute uncertainty to the measured value
  • Percentage uncertainty: relative uncertainty expressed as a percentage

Significant Figures

• Significant figures (sig figs) represent the number of digits in a measurement that are known with certainty:
  • Non-zero digits are always significant
  • Zeros between non-zero digits are significant
  • Leading zeros are not significant
  • Trailing zeros are significant only if the number contains a decimal point

Test your knowledge of fundamental and derived units, prefixes, measurement uncertainty, and significant figures in physics. Learn the basics of physics measurements and calculations.