Physics Lab Report 3

Topics: Pendulum, Analytic geometry, Dimension Pages: 7 (918 words) Published: December 4, 2014

Physics Lab Report#3

“Determining the period of a pendulum”

Name: Fei Huo

Date performed: October 1st, 2014

Period 5

Teacher: Mr. Glasel

The Purpose of this Lab was so that my classmates and I can examine what kind of factors affect the period of a pendulum.

In a simple form, the pendulum is a weight hung from a long string that Galileo discovered that it can be used to track the passage of time very accurately around 400 years ago. In this lab my classmates and I are using the pendulum to determine the value of the accelerations of any object due to gravity.

1) First, you measure the string on the pendulum at 1.0m (meters) long and measure from the pivot point to the center of the mass by using the protractor. 2) Then, displace the bob string to an angle of 20 degrees from its resting position and measure the time required for the bob to complete 20 complete cycles swinging back and forth with the stop watch provide (repeat this process for the pendulum lengths of 0.80m, 0.60m, 0.40m, and 0.20m and keep all other factors constant). 3) Third, record all the data that you got into Table 1.

4) Forth, measure the string at 0.50m and always displace the bob 20 degrees. 5) Fifth, Measure the amount of time to complete 20 swings for the different mass bobs (aluminum, steel, brass, lead, and wood). 6) After when you completed step 5, record the data into Table 2. Sixth, start the bob displaced at 30 degrees and measure the amount of time to complete 20 complete cycles; repeat this procedure for an arc of swing of 25 degrees, 20 degrees, 15 degrees, and 10 degrees. 7) Finally, answer the questions.

Data Tables #1:

Length (m)
Time for 20 cycles(s)
T=Period (s)
39 s
1.95 s

35 s
1.75 s

31 s
1.55 s


25 s

1.25 s

19 s
0.95 s

Data Table #3:

Arc of swing ()
Time for 20 cycles (s)
28 s
1.4 s
28 s
1.4 s
28 s
28 s


28 s

Data Table #2:

Bob Material
Mass of Bob (kg)
Time for 20 cycles (s)
T=period (s)
0.0064 kg
27 s

1.35 s
0.024 kg
28 s

1.4 s
0.0669 kg
28 s

1.4 s


27 s
1.35 s
28 s
1.4 s

1a. As the length of the string increased, did the period (T) increased, decrease, or remain the same? The period increase when the length of the string increased.

1b. As the mass increased, did the period (T) increased, decrease, or remain the same? The period remained the same as the mass increased.

1c. As the arc of swing increased, did the period (T) increased, decreased, or remained the same? The period of swing decreased as the period (T) increased.

2a. from the data table 1 construct a graph of period2 (T) (Y axis) vs. Length (m) (X-axis)

2b. From data table 2 construct a graph of period (T) (Y axis) vs. Mass (kg) (X Axis)
2c. from data table 2 construct a graph of period (T) (Y axis) vs. Arc of swing (°) (X axis)

3. For each of these three graphs, describe the relationship between the Period and the X-axis variable.

If the graph is horizontal straight line then the two variables are independent of each other. If the graph is a straight diagonal line the relationship is linear. (i.e., the variables are directly proportional to each other). Length/ Period is Linear

Arc of Swing/ Period is Independent Variables
Material/Period is Linear

4. What other factors(s), not investigated by you (length, mass, arc of swing) in this experiment might affect the period of the pendulum? The angle of the Pendulum’s swing

5. What is the advantage of timing 20 complete swings of your pendulum instead of only one? The timing of 20 complete swings of my pendulum can have a more accurate measurement since there is less...
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