paper 3

• Fiducial marker


  A card used as a reference point
• Placement of fiducial marker

  • Should be below the bob, with the mark on the card at the edge of the bob when hanging straight
• Measuring amplitude


  Use a set square and ruler to measure distance between edge of bob at equilibrium and amplitude
• Calculating mean


  Omit any anomalous values, then divide sum of remaining values by number of values
• Percentage uncertainty in mean

  Absolute uncertainty (half the range) divided by mean, multiplied by 100
• Differences in values of s (vertical deflection) between loading and unloading are due to random error
• Thinner beam of same material

  Causes greater values of s (vertical deflection) with same loads, resulting in smaller percentage uncertainty
• Disadvantage of thinner beam is it could deform plastically, causing the graph to not be linear
• Measuring internal resistance and emf


  1. Use voltmeter across battery

  2. Use ammeter in series

  3. Plot v vs i graph

  4. Gradient = -r, y-intercept = epsilon