Physics: Measurement

Physics: Measurement

1. Quantities

   • Basic quantities
     • Definition: A physical quantity that cannot be defined in terms of other physical quantities.
     • Length (m)
     • Time (s)
     • Mass (kg)
     • Temperature (K)
     • Luminous Intensity (cd)
     • Amount of substance (mol)
     • Electric Current (A)
   • Derived Quantities
     • Definition: A physical quantity that is derived from basic quantities. (no standard definition)
     • Density (p, rho) = mass/volume
     • Momentum = mass x velocity
     • Force (N) = mass x acceleration
     • Pressure (Pa) = force/area
     • Work done (J) = force/displacement
     • Power (W) = work done/time

2. Uncertainty

   • Is the extent of precision of the measurements taken with the intrument.
   • Determined according to the smallest division/graduation on the instrument's scale (in other words, its precision).
   • Measuring instruments, their smallest division and their uncertainty
     • Meter rule - 0.1 cm Uncertainty: +/- 0.1 cm
     • Vernier Caliper (20 division) - 0.05 cm Uncertainty: +/- 0.01 cm
     • Vernier Caliper (10 division) - 0.01 cm Uncertainty: +/- 0.02 cm
     • Micrometer Screw Gauge - 0.01 mm Uncertainty: +/- 0.01 mm
     • Thermometer - 0.5 °C Uncertainty: +/- 03°C (for temperature reading) & +/- 0.5°C (for temperature change)
     • Stopwatch - 0.01 s Uncertainty: +/- 0.02 s
     • Electronic Mass Balance - 0.01 g Uncertainty: +/- 0.01 g