(1.1) Use of SI Units and Their Prefixes

• What are the fundamental SI units for mass?

  kg (kilograms)
• What is the SI unit for length?

  m (metres)
• What is the SI unit for time?

  s (seconds)
• What is the SI unit for the amount of substance?

  mol (moles)
• What is the SI unit for temperature?

  K (kelvin)
• What is the SI unit for electric current?

  A (amperes)
• How can SI units of quantities be derived?

  By using their equations, e.g., F=ma
• What are the SI units of force (F)?

  kg m s$^{-2}$ (also known as N)
• How are the SI units of voltage derived?

  By using energy and charge equations
• What is the formula for energy in terms of mass?

  E=½ m v$^{2}$
• What are the units for charge (Q)?

  As (ampere seconds)
• How do you convert from mega electron volts to joules?

  Multiply by 1.6 x 10$^{-19}$
• How do you convert 76 MeV to joules?

  1.216 x 10$^{-11}$ J
• What is the conversion factor for 1 kWh to joules?

  3.6 x 10$^{6}$ J
• What is a random error?

  It affects precision and causes measurement spread
• How can random errors be reduced?

  By taking at least 3 repeats and calculating a mean
• What is a systematic error?

  It affects accuracy and causes consistent bias
• How can systematic errors be reduced?

  By calibrating apparatus with known values
• What is the meniscus in liquid measurement?

  The central curve on the surface of a liquid
• How should the meniscus be read to reduce error?

  At eye level to reduce parallax error
• What is the difference between precision and accuracy?

  • Precision: Consistent measurements around a mean
  • Accuracy: Measurements close to the true value
• What is repeatability in experiments?

  • Same results when repeated by the original experimenter
  • Uses the same equipment and method
• What are the methods to reduce random and systematic errors?

  Random Errors:

  • Take multiple measurements
  • Use data loggers

  
  

  Systematic Errors:

  • Calibrate equipment
  • Correct for background radiation