Name: Sally Example Date: mm/dd/yy Science period: # Lab Report: Frequency vs. The Starting Angle of a Pendulum Experimental Problem: This experiment is to determine the effect of the starting angle of a pendulum on the frequency of its swing. Background Information A pendulum is an object suspended from a fixed point, which when pulled and let go, swings from side-­‐to-­‐side in a regular periodic motion. A pendulum cannot swing by itself, it needs an initial force (pull), and that pull has an angle. An angle is a figure formed by two lines that start at the same point. It is measured in degrees. The starting angle will be changed four times to see how it affects the frequency. The frequency in this investigation will be the number of swings per 30 seconds. Manipulated (Independent) Variable (X) The starting angle, measured in degrees. Responding (Dependent) Variable (Y) The frequency, measured in swings per 30 seconds. Experimental Controls The length of the string on the pendulum (20.5 cm) The predetermined time in which swings will be counted (30 seconds) The size of the bob (mass) of the pendulum (1 cm in diameter) The fixed point (pivot) Hypothesis If the starting angle of a pendulum is larger, which will cause the bob to travel a longer distance from left to right, and the number of times the pendulum travels from the starting point and back is calculated in thirty seconds, then the frequency (number of swings/ 30 seconds) should be lower than with a smaller starting angle. EXPERIMENT Materials -­‐ String (22 cm) -­‐ Paperclip (small) -­‐ Small bob (1 cm in diameter) -­‐ Protractor -­‐ Stop-­‐watch -­‐ Tape -­‐ Pencil (7 cm) Adapted from a posting by Arizona School for the Arts. Copyright 2011. <https://sites.google.com/a/goasa.org/guttell-­‐science/lab-­‐report-­‐handbook> Name: Sally Example Date: mm/dd/yy Science period: # Procedures 1. Tie the string around the bob. 2. Tape the pencil to a table, sticking out just enough to hang the pendulum. 3. Using the protractor, angle it to 20 degrees. 4. Let go of the string and count the frequency (swings) for 30 seconds. 5. Record your data in the data table. 6. Increase the angle by 20 degrees and repeat steps 4-­‐5. 7. Repeat step 6 two more times for a total of 4 different starting angles. 8. Repeat the experiment two more times for accuracy of the results and record the findings in the data table. Starting Angle (degrees) Frequency (swings/30s) Frequency (swings/30s) Frequency (swings/30s) Frequency (swings/30s) Trial 1 Trial 2 Trial3 Average 20 degrees 55 57 57 56.3 40 degrees 55 56 55 55.3 60 degrees 56 64 54 58.0 80 degrees 59 61 51 57.0 Adapted from a posting by Arizona School for the Arts. Copyright 2011. <https://sites.google.com/a/goasa.org/guttell-­‐science/lab-­‐report-­‐handbook> Name: Sally Example Date: mm/dd/yy Science period: # Conclusion The problem of this experiment was to determine the effect of the starting angle of a pendulum on the frequency of the swinging pendulum. When comparing the pendulum with a starting angle of 40˚ and 60˚, the frequency went from 55 times/30 seconds to 58 times/30 seconds, which contradicts the hypothesis, which stated that if the starting angle was larger then the frequency would be lower. However, when comparing the pendulum with a starting angle of 60˚ and 80˚, the frequency went from 58 times/30 seconds to 57 times/30 seconds, which supports the hypothesis. Since this investigation showed inconclusive results, there may have been factors that affected the results. One source of error was that there was a fan in the room that may have caused extra swings and altered the outcome. Making sure that nothing interferes with the pendulum is crucial for this experiment. If the experiment was repeated, a survey of the room would be good, where everything that may cause problems, are taken out of the room. The next two experiments also involve pendulums, so it will be helpful to adjust the room accordingly. This investigation led itself to questioning other scenarios like, what if I change something else about the pendulum, will that affect the frequency? For example, if instead of the string a rod is used, would that increase or decrease the frequency? Here is a picture of the experiment set-­‐up: Adapted from a posting by Arizona School for the Arts. Copyright 2011. <https://sites.google.com/a/goasa.org/guttell-­‐science/lab-­‐report-­‐handbook>