# Lab 5

Topics: Pendulum, Orders of magnitude, Tape measure Pages: 5 (1158 words) Published: March 31, 2015
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GS104
Lab Report
Experiment # 5
Pendulum and the Calculation of g
David Case:
February 14, 2015

Experiment #5
Pendulum and the Calculation of g

Objectives:
To calculate the acceleration due to gravity by observing the motion of a pendulum. To investigate the effect of varying mass on the period of a pendulum. To investigate the effect of varying the length of a pendulum on the period Materials:

stopwatch support for the pendulum

tape set of washers

protractor spring scale
tape measure weight bag

Lab Notes:

1. Changing the amplitude:
A. Length:
1. Attach a small plastic bag to the spring scale.
2. Add washers to the plastic bag until the scale measures approximately 25 g total. The filled bag will hereafter be referred to as the bob. Record this value as “Mass of bob” in the place provided in Data Table 1. Table 1: Trial of values at varying degrees

Length of string: 100cm= 1 m Mass of bob: 25g= 0.025kg Placement of Bob Degrees
Amplitude (bob horizontal displacement) cm
Trial 1 (s) 5 cycles
Trial 2 (s) 5 cycles
Trial 3 (s) 5 cycles
Avg. Time (s) 5 cycles
Period 1 cycle

6
10.00
10.11
10.62
10.24
2.04
10°
15
9.45
9.68
9.55
9.56
1.91
15°
23
9.54
9.69
9.86
9.69
1.96
20°
34
10.06
9.99
9.91
9.98
1.99
25°
39
9.77
9.81
9.67
9.75
1.95
30°
46
9.75
10.12
9.92
9.93
2.01

3. Measure a piece of string that is approximately 120 cm in length. Tie the string around the top of the bag so that the washers cannot fall out. Suspend the bob from this string so that it measures exactly 1 m (100 cm) between where it attaches to the support and the bottom of the bob. 4. Use tape to affix the protractor behind where the string is attached to the support so you can measure the pendulum’s amplitude in degrees. The center hole in the protractor should be located directly behind the pivot point. The string should hang straight down so that the string lines up with the 90o mark on the protractor. 5. Stretch the measuring tape horizontally and use tape to affix it to the wall or door so that its 50-cm mark is directly behind the bob at rest. 6. Displace the bob out to the 5o mark and hold it there. Then observe the bob’s location during its first cycle as it swings relative to the tape measure and record the distance in centimeters as “Amplitude (bob horizontal displacement)” in Data Table 1. 7. With a stopwatch ready to begin timing, release (do not push) the bob and begin timing how long it takes the bob to move through five complete cycles. Record this first trial time in Data Table 1 for Trial 1. Repeat the procedure for the second and third trials. Then average the three trial times to calculate the average period for one cycle, and record this value in Data Table 1. 8. Repeat this procedure, releasing the bobs at 10°, 15°, 20°, 25°, and 30°, and recording.

Part 2: Changing the mass
9. Add more weights to the bag until the mass has doubled to approximately 50 g. Record this value as “mass of bob” in grams into the line provided next to Data Table 2. 10. Repeat the procedure used in Part 1 using only a 10o amplitude for the starting point of the bob. Record the data in Data Table 2. Data Table 2: Trial values for bob masses

Bob weight (g)
Bob weight (kg)
Trial 1
Trial 2
Trial 3
Avg Time (s)
Period
50
0.05
9.33
10.02
9.59
9.65
1.94
50
0.05
9.71
9.76
9.79
9.75
1.95

Part 3: Changing the length of string
11. Remove the weights until the original mass used in Part 1 (approximately 25 g) is inside the bag. Record this “mass of bob” in grams into the line provided next to Data Table 3. 12. Put the original bob containing the washers back onto the pendulum. Use a 10o amplitude and perform three trials each with successively shorter lengths of string. For...