Taking and recording measurements

You will need to create a table for recording your results.

  • Usually the independent variable (the force in this investigation) is written down in the left hand side column.
  • The table needs to have full headings with correct units.
  • Unless you are told that repeating results isn’t necessary, the table should show a certain number of repeats and include a column for a mean calculation.
  • The measured results should all be written in the table to the same number of decimal places that match the precision of the measuring instrument. Digital ammeters, voltmeters and stop clocks usually read to the nearest 0.01 of a second, therefore you must record the full reading of the instrument, eg 1.32 s, not 1.3 s or 1 s.
  • The table should contain enough values of the independent variable to allow the original prediction to be tested.
  • You should try to use the greatest range possible without damaging the apparatus (for example, don’t overstretch the spring, or put too much voltage across a bulb).

Your table could look similar to this one.

A 7 column table labelled Force (N), Time for 10 rotations (s) and Mean time for 10 rotations (s). The second column is further divided into Group 1, Group 2, Group 3, Group 4 and Group 5.

Once the results have been written down, you will need to check if any of the readings are anomalous.

All the readings going across the table should be reasonably similar if they are repeatable. If any result is much higher or lower, it should be crossed out, and not included in the mean calculation for that row.

If time permits it is good practice to repeat the reading so the anomalous reading can be replaced. You will need to do this before you plot the graph in section B of the practical assessment.