Tuesday, March 12, 2013

Experiment 4: Standing Waves

       The purpose of this lab is to observe and analyze standing waves on a string that is under a tension and driven by an oscillator.

Experiment:
The experiment is set up as shown below
One end of the string is attached to a hanging mass and the other end
is attached to an oscillator connected to a frequency generator.
To create a standing wave, we can adjust the frequency generator.

Data and Analysis:
Length of string
1.954 ± 0.02 m
Mass of string
0.00206 ± 0.00001 kg
Linear density
0.001054 ± 1.55E-5 kg/m

1, 2, and 3.
Case 1
Harmonics
(n-value)
Frequency (Hz)
# of Nodes
Distance between nodes (m)
Wavelength (m)
1
15 ±2.5
2
1.522 ± 0.01
3.044 ± 0.01
2
30 ± 2.5
3
0.761 ± 0.01
1.522 ± 0.01
3
43 ± 2.5
4
0.507 ± 0.01
1.015 ± 0.01
4
61 ± 2.5
5
0.381 ± 0.01
0.761 ± 0.01
5
73.4 ± 0.1
6
0.304 ± 0.01
0.609 ± 0.01
6
87.9 ± 0.1
7
0.254 ± 0.01
0.507 ± 0.01
7
102.9 ± 0.1
8
0.217 ± 0.01
0.435 ± 0.01
8
117.2 ± 0.1
9
0.190 ± 0.01
0.381 ± 0.01
9
131.6 ± 0.1
10
0.169 ± 0.01
0.338 ± 0.01
10
146.5 ± 0.1
11
0.152 ± 0.01
0.304 ± 0.01














Calculated speed: 43.14 ± 0.86 m/s
Speed from graph: 44.39 ± 0.2982 m/s

Case 2
Harmonics
(n)
Frequency
(Hz)
#of Nodes
Distance between nodes (m)
Wavelength
(m)
1
7.4 ± 0.1
2
1.522 ± 0.01
3.044 ± 0.01
2
15.0 ± 0.1
3
0.761 ± 0.01
1.522 ± 0.01
3
23.0 ± 0.1
4
0.507 ± 0.01
1.015 ± 0.01
4
30.3 ± 0.1
5
0.381 ± 0.01
0.761 ± 0.01
5
36.9 ± 0.1
6
0.304 ± 0.01
0.609 ± 0.01
6
45.5 ± 0.1
7
0.254 ± 0.01
0.507 ± 0.01














Calculated speed: 21.55 ± 1.25 m/s
Speed from graph: 22.92 ± 0.3424 m/s

4. Ratio of wave speeds for case 1 compared to case 2 is 1.94. This ratio is really close to the predicted wave speed which is 2.


5. Case 1
Harmonics
Frequency (Hz)
n*f1 (Hz)
% Difference
1
15
15
0.00%
2
30
30
0.00%
3
43
45
4.44%
4
61
60
1.67%
5
73.4
75
2.13%
6
87.9
90
2.33%
7
102.9
105
2.00%
8
117.2
120
2.33%
9
131.6
135
2.52%
10
146.5
150
2.33%
The table above shows that the measure frequencies for case 1 is close to nf1

6.
Harmonics
Case 1 Frequency
Case 2 Frequency
F1/F2
1
15
7.4
2.0
2
30
15
2.0
3
43
23
1.9
4
61
30.3
2.0
5
73.4
36.9
2.0
6
87.9
45.5
1.9
The ratio of the frequency of the harmonics for case 1 and case 2 is 2, which is also the ratio between the speed of the wave for case and case 2.

Some sources of error that may affect the results of this experiment are:
- Error contributed to equipment and measuring tools such as ruler and balance
- Error contributed to the first frequency generator we used which is not digital and has a large increments.

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