Motion of a simple pendulum

Use a simple pendulum to test SHM and measure the value of g.

  1. Set things up so that a 50-gram mass hangs from a long piece of string. Run the string through one of the holes in the 3-knob bar, and wrap one or two loops around a knob to hold it in place. Make sure that you can swing the mass freely when the string is 80 cm long.
  2. Make measurements with at least 4 different lengths L, ranging from about 7 cm to about 80 cm. Measure the time to swing back-and-forth 10 times with small angular amplitude: start at an angle of about 10 degrees from the vertical. Make 2 trials at each length.
  3. Make a neat table with your results, showing the period, and period squared, in each case.
  4. Create one graph with your data. Make a graph of the period squared versus the length of the string.
  5. Determine the slope of line connecting your measurements and the uncertainty in the slope.
  6. Use the slope (and uncertainty) to compute a value for the local acceleration due to the gravity (and its uncertainty). Does your value agree with the standard one?
If you have time ...
  1. Use your graph to find the length of a pendulum which would have a period of exactly one second. Does that length have any significance?
  2. What is one simple modification you could make to improve the precision of your value of g?