03. Measurement of g by freefall

  • 00:43 What is the difference between precision and accuracy?
  • 01:25 No measurements made here should be used as results. Why?
  • 01:38 What is meant by the term parallax?
  • 01:42 This test should be performed at least three times. Why should we conduct the measurement three times?
  • 01:48 Which is the dependent variable? What other measurements could we make?
  • 01:55 What range of measurements should be used?
  • How many: different height measurements should be used?
  • How many: repeat measurements should be made at each height?
  • 02:01 What is plotted on the:
    - x-axis?
    - y-axis?
  • 02:05 As we have only completed one set of measurements we do not yet know if the graph will be a straight line or a curve?
  • How many points needed for a: - straight line? - curve?
  • Should the graph be a curve or a straight line?
  • 02:34 The measured gradient is equal to ½ of the value of g. Why?
  • 02:40 What improvements do you think could be made to the method in this experiment?
  • metal sphere

  • electromagnet

  • magnetic Switch SPST

  • electronic timer

  • metal plate

  • break contact

  • metre rule or tape measure with millimetre resolution

  • power supply, low voltage DC

  • leads and connectors

  • graph paper, pencil, ruler etc.

  • retort stand and boss (to hold the electromagnet)

Hazard Risk Control measure

Contact with the ball

If the ball misses the plate it can cause injury to the body

Provide an up-turned box lid to catch the ball after its fall.