UNITS

• Physical quantities and units


  The foundation of physics, enabling scientists to describe, measure, and analyze the world around us
• Physical quantity is any property or attribute that can be measured and expressed numerically
• Examples of physical quantities

  • Length
  • Mass
  • Time
  • Temperature
  • Velocity
  • Energy
  • Electric charge
• Base quantities and supplementary quantities in physics curriculum

  • Length
  • Mass
  • Time
  • Amount of substance
  • Temperature
  • Current
  • Luminous Intensity
  • Plane Angle
  • Solid Angle
• SI (International System of Units)


  A globally recognized and standardized system of units that set the foundation for scientific measurements across various disciplines
• SI units for base quantities

  • Meter (m)
  • Kilogram (kg)
  • Second (s)
  • Mole (mol)
  • Kelvin (K)
  • Ampere (A)
  • Candela (cd)
• SI units for supplementary quantities

  • Radian (rad)
  • Steradian (sr)
• Radian


  The plane angle subtended at the center of a circle by an arc length which is equal to the radius of the circle
• Steradian


  The solid angle subtended at the center of a sphere by an area on its surface equal to the square of its radius
• Derived physical quantities from base quantities

  • Area
  • Volume
  • Density
  • Velocity
  • Acceleration
  • Momentum
• Derived units


  • Force (newton, N)
  • Pressure (pascal, Pa)
  • Energy, Work (joule, J)
  • Power (watt, W)
  • Frequency (hertz, Hz)
  • Electric Charge (coulomb, C)
  • Electromotive force (volt, V)
  • Electrical Resistance (ohm, Ω)
  • Electrical Conductance (siemen, S)
  • Permeability (henry, H)
  • Capacity (farad, F)
  • Magnetic flux (weber, Wb)
  • Magnetic flux density (tesla, T)
• When terms of an equation are physical quantities, they should have the same unit
• Units should not be written in plural form
• Prefixes should be used for all units except those named after people
• The first letter of all name units must be in lowercase
• Units should always be written after the amount, separated by a space
• The SI unit of energy is the joule (J).
• Work done = force x distance moved in direction of force

  
• Energy can be transferred from one object to another by work done or heat transfer.