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course phy 231
quicklab1#$&*
course phy 231
Brief pendulum experimentUses: washer, thread, analog clock, ruler or meter stick
Construct a pendulum using washer and thread. Make 1-minute counts for pendulum lengths (measured from the position at which the thread is held to the center of the washer) equal to three different lengths:
• the the distance from your wrist to your fingertips
• the distance from your elbow to your fingertips
• the distance from your shoulder to your fingertips
Be sure to measure the length of each pendulum you time.
Report the pendulum lengths and the corresponding numbers of counts:
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Wrist to fingers: 8 inches, 63 full swings in 1 minute
Elbow to fingers: 18 inches, 41 full swings
Shoulder to fingers: 28 inches, 35 full swings
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Analysis:
Graph your 1-minute count vs. length, and sketch a smooth curve representing the trend of your data.
Using your graph estimate the number of counts for a pendulums of length 52 cm, and another of length 13 inches. Estimate also the lengths corresponding to pendulum counts of 30 and 50.
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Using my graph, for 52 cm length, I got 16.3 full swings
Using the graph, for 13 cm length, I got 52 full swings
For 30 counts using the graph, the required length would have to be 31 cm
For 50 counts, the length would have to be
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Determine the period of each of your three pendulums, i.e., the time required to complete 1 oscillation. A oscillation is from extreme point through equilibrium to opposite extreme point.
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For the 8 cm length, a period was .95 seconds
For the 18 cm length, a period was 1.46 seconds
For the 28 cm length, a period was 1.71 seconds
Inches rather than centimeters, according to your data report; the periods look just about right if lengths are in inches.
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Sketch a graph of period vs. length, showing your three points, and sketch a smooth curve to fit your graph.
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The curve y=-.0013x^2+.085x+.355 fits well
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Use your graph to estimate the period of a pendulum whose length is 26 cm, and also the length for which the period would be 1.2 seconds.
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Using the graph for length of 26 cm, the period should be 1.7 seconds
For period of 1.2 seconds, the corresponding length should be 12.2 cm
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What is the uncertainty in the number of counts made, and to what do you attribute the uncertainty?
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Counts? I’m confused. What do you mean by counts?
You originally counted the number of cycles in a minute, for each length.
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What is the approximate average percent uncertainty in your counts?
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Do your sources of uncertainty result in the same expected percent uncertainty for all counts?
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Good. However see my last note and submit a revision. Only those last three questions need to be answered.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
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