Foundations of Physics

Foundations of Physics

1. International System of Units (SI)

   • Developed so that scientists all around the world could work with one system of measurements
   • Base Quantities
     • One of the 7 fundamental physical quantities that can be used to describe all other quantities
     • Mass
     • Length
     • Time
     • Current
     • Amount of Substance
     • Temperature
     • Luminosity
   • Base Units
     • The units of base quantities
     • Kilogram (kg)
       • Mass
     • Metres (m)
       • Length
     • Seconds (s)
       • Time
     • Amperes (A)
       • Current
     • Mole (mol)
       • Amount of substance
     • Kelvin (K)
       • Temperature
     • Candela (cd)
       • Luminosity
   • Derived Quantity
     • A quantity derived from a combination of base quantities
     • Force
     • Pressure
     • Charge
     • Power
     • Voltage
     • Energy
     • Frequency
     • Others (see note)
       • Area Volume Density Velocity Acceleration Work
   • Derived Unit
     • Units of derived quantities
     • Newton (N)
       • Force Can be written as kgms^-2
     • Pascal (Pa)
       • Pressure Can be written as m^-1kgs^-2
     • Coulomb (C)
       • Charge Can be written as sA
     • Watts (W)
       • Power Can be written as m^2kgs^-3
     • Volts (V)
       • Volts Can be written as m^2kgs^-3A^-1
     • Joules (J)
       • Energy Can be written as kgm^2s^-2
     • Hertz (Hz)
       • Frequency Can be written as s^-1
     • Others (see note)
       • m^2 (Area) m^3 (Volume) kgm^-3 (Density) ms^-1 (Velocity) kgms^'1 (Momentum) ms^-2 (Acceleration) kgm^2s^-2 (Work)

2. Prefixes

   • Smaller
     • Pico
       • x10^-12
     • Nano
       • x10^-9
     • Micro
       • x10^-6
     • Milli
       • x10^-3
     • Centi
       • x10^-2
     • Deci
       • x10^-1
   • Bigger
     • Mega
       • x10^6
     • Kilo
       • x10^3
     • Giga
       • x10^9
     • Tera
       • x10^12

3. Uncertainty

   • Percentage uncertainty = (absolute uncertainty / average measurement) x 100
   • If you are multiplying or dividing quantities, the total percentage uncertainty is the sum of each percentage uncertainty

4. Percentage Difference

   • ((accepted value - measured value) / accepted value) x 100

5. Graphs

   • Straight line graphs
     • y = mx + c
     • m (gradient) = change in y / change in x
     • c is the y intercept when x=0