Unit 1: Physical Quantities and Units

• Physical quantities must be comprised of a numerical magnitude and a unit
• Examples of physical quantities include:

  • 3A (3 amperes of current)
  • 20N (20 Newtons of force)
  • 80J (80 Joules of energy)
• Estimation skills are important for scientists and engineers as they allow for the validation of calculations
• SI units are the fundamental (base) units of physical quantities
• The SI unit of mass is Kilograms (kg)
• The SI unit of current is Amperes (A)
• The SI unit for temperature is Kelvin (K) as it is the absolute scale for temperature
• The SI unit of length is Metre (m)
• The quantity with an SI unit of seconds (s) is Time
• Newtons (N) are not SI units; the SI units for force are kgms^-2
• The SI units of force are kgms^-2
• The SI units of energy are kg m^2 s^-2
• 60TΩ in standard form is 6 x 10^13
• 0.000003m with a suitable prefix is 3μm (3 x 10^-6 m)
• The actual value of 8MΩ is 8,000,000Ω or 8 x 10^6 Ω
• 6000pF in nF is 6nF (1 nF = 1000 pF)
• The multiplier associated with the prefix kilo (k) is x1000 (10^3)
• 7GΩ in standard form is 7 x 10^9 Ω
• A homogeneous equation has the same SI base units on both sides of the equals sign
• The two main categories of experimental error are Systematic Error and Random Error
• Systematic error affects measurements consistently, causing them to be higher or lower than the true value by a constant amount
• Causes of systematic error include parallax error, zero error, incorrect apparatus setup, and faulty equipment
• To avoid systematic error, readings should be taken at the appropriate level, balances should be zeroed correctly, apparatus should be set up correctly, and faulty equipment should be replaced
• Random error affects measurements variably upon repetition, causing them to be higher or lower than the true value by varying amounts
• Causes of random error include human error and small inconsistencies in equipment behavior
• To minimize random error, repeat readings should be taken and averaged, and any anomalous results should be disregarded
• A scalar quantity has only magnitude
• A vector quantity has magnitude and direction
• Acceleration is a vector quantity
• Mass is a scalar quantity
• How to check if an equation is homogeneous: Reduce both sides to their SI base units and see if they match