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the tension τ of that mass on the string. We can find the tension by (36)
where mw is the mass of the weight. Thus plugging this information into equation (31) we can claim that
the velocity of the wave on the string is (37) ⁄ (38) This will be the theoretical value for the velocity. You will then use data studio to find the first three
harmonic frequencies of the string. The first harmonic frequency will have 2 nodes and 1 antinode. Using
this information you will use equation (22) to calculate the wavelength λ of each harmonic frequency. The
first harmonic frequency has n=1, the second harmonic has n=2, and the third harmonic has n=3. Now
that you know the wavelength, you will be able to check on the accuracy of your measurement of the
distance between the nodes by using the fact that the distance between nodes is always half the
wavelength. For the last part of this part of the experiment, you will find the measured velocity of the
wave in the string by using the measured harmonic frequency and the corresponding wavelength for that
frequency. Then you will plug these two pieces of information into (39)
to get the velocity of the wave.
4.2 The Resonance Tube
For the final part of the experiment, you will find the speed of sound in a resonance tube. You
will start by finding the theoretical speed of sound using 331 0.62 ⁄ (40) where T is in Celsius. Next, you will record the position of the plunger L and the number of nodes in the
tube. This is a closed tube thus we number of nodes and antinodes is shown in Figure 6. 10 We can now find the wavelength using 4 for 1, 3, 5, … (41) where n is the number of nodes. Now that we have the wavelength, you will find the measured speed of
sound using equation (40). The frequency that you will use is either 1200 Hz or 1800 Hz depending on
which run you are doing. Your calculated speed of sound should be very close to your measured speed
of sound. Figure 6 The nodes and antinodes of the resonance tube as the plunger is pulled back. Here overtone is the same as
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This document was uploaded on 03/20/2014 for the course PHYS 215 at Lafayette.
- Fall '09