Natural Science Unit 29 Laboratory Activity: Galilean Mechanics - The Pendulum

Goal: Measure the value of gravitational acceleration.

Materials and Equipment:

• Several masses; if you use coins, it is easy to double or triple your mass.
• Strong string or nylon fishing line, able to support your weight without breaking.
• 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.

Procedure:

1. Weigh your masses.
2. Tie them to the end of the string.
3. Tie the string to your hook.
4. Measure as accurately as possible the distance between the hook and the center of the masses; this is your pendulum length L.
5. Displace the pendulum (measure the horizontal distance x of the displacement of the pendulum from its rest position.)
6. Find your pulse on your wrist.
7. Count the number of pulse beats required for the pendulum to make 10 complete back-and-forth swings (10 periods). Record the number.
8. Repeat at least twice, and average the number of pulse beats.
9. Repeat your experiment, varying the mass. Does the number of pulse beats needed for 10 complete swings change?
10. Repeat your experiment, varying the length of the string by at least 25%. Does the number of pulse beats required for 10 complete swings change?
11. Repeat all your measurements, using a stopwatch to time the swings.

Report

1. Describe your experimental setup. Did you make any changes to the described procedure because of availability of equipment? Did you do anything to increase the accuracy of your measurements.
2. Present your data and calculations in a useful tabular form. Clearly distinguish between measured values and calculated values. Give at least one example of each type of calculation you perform.
3. Explain which factors (length of the string, mass of the weight, etc) affect the period of the pendulum and which do not.
4. Was your pulse a good way to see the differences, or did you need the stopwatch?

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