Lab: Pendulum Motion 2
Goal: To determine the dependence of the pendulum period on mass, string length.
NOTE: This lab is similar, but different in goal from the Pendulum Lab Part 1. In that lab, we took the formula T = 2π √ (L/g) as a given; here we will try to understand how it was derived.
- At least 3 different masses (you could use coins, which makes it easy to double or triple masses). Masses should vary by at least 25%.
- A least 3 lengths of strong string or nylon fishing line, able to support your weight without breaking. String lengths should vary by at least 25%.
- Hook on which to tie pendulum; should be fastened to make the pendulum as long as possible (I used the ceiling hook for a hanging plant).
- Stopwatch or watch with second hand.
- Weigh your masses.
- Tie the least massive to the end of the shortest string length you have.
- Tie the string to your hook.
- Measure as accurately as possible the distance between the hook and the center of the masses; this is your pendulum length L.
- Displace the pendulum (measure the horizontal distance x of the displacement of the pendulum from its rest position.)
- Measure the length of time required for the pendulum to make 10 complete back-and-forth swings (10 periods). Determine the value of T.
- Repeat at least twice.
- Repeat your experiment for each mass, but the same string length.
- Repeat your experiment for each mass, for the next string length, until you have done a complete sequence (all available masses for all available string lengths) at least three times each.
- Present your data in an organized tabular form.
- Plot your data in a reasonable fashion: for example, plot the variation in period as a function of mass for each individual string length, then plot the period (separately) for each string length and mass.
- Does the period change when you changed the mass? How might this affect your previous lab calculation for the gravitational acceleration?
- Does the period change when you changed the length? How might this affect your previous lab calculation for gravitational acceleration?
- Show how your results support or contradict the formula used to determine gravitational acceleration in the previous lab by solving T = 2π √ (L/g) for g.
- Describe your materials, equipment, an dprocedures in sufficient detail that your fellow students could repeat your experiment.
- Report your data. Be sure to indicate the amount of error in your measurements. For example, if you can only measure a mass of 25 gms within 1 gm, your error would be 25 ± 1, or 1/25 = 4%.
- Present your data in an organized form, preferably in a table, in such a way it is easy to compare results as you repeate trials or vary a specific contributing factor.
- Show a sample calculation for your calculated values.
- Show your graphs of period vs. mass and period vs. string length.
- You may use a spreadsheet to calculate your information and create your table.
- Summarize your results.
- Draw conclusions about what is happening.
- Suggest at least one way to improve your experiment.
Upload your report to the Moodle Lab Assignment for this Lab.
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