PASCO WA-9857 Instruction Manual

String vibrator

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Instructions

Instruction Manual

Demonstrations

Experiments

No. 012-08798A

Sample Data

String Vibrator

WA-9857

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Page 1 Instructions Instruction Manual Demonstrations Experiments No. 012-08798A Sample Data String Vibrator WA-9857...
Page 2: Table Of Contents
String Vibrator Model No. WA-9857 Contents Introduction..............3 Equipment Setup .
Page 3: Introduction
Introduction The PASCO scientific WA-9857 String Vibrator drives a string or elastic cord to produce a standing wave. With it, you can study frequency, wavelength, and resonance, as well as the factors that affect those properties. It is well-suited for classroom demonstrations and hands-on experiments.
Page 4: Equipment Setup
3 cm (1¼ inch). The PASCO Small C-Clamp (SE-7286, 6-pack) can clamp the String Vibrator to tables up to 5 cm (2¾ inches) thick; the Large C-Clamp (SE-7285, 6-pack) accommodates tables up to 7 cm (2¾...
Page 5 Model No. WA-9857 Equipment Setup Rod Clamp The case of the String Vibrator has a built-in rod clamp for mounting it either horizontally or vertically on a rod with a diameter up to 12.7 mm (1/2 inch). Slide the rod through the case in the preferred orientation and tighten the thumb screw.
Page 6 String Vibrator Equipment Setup Vertical String The vertical arrangement with the elastic cord makes a good classroom or lecture demonstration. It requires a vertical rod and a horizontal component at the top of the rod, such as a Pendulum Clamp (SE-9443), to attach the elastic cord.
Page 7 Model No. WA-9857 Equipment Setup Good Nodes Versus Bad Nodes Most demonstrations and experiments involve adjusting the length, tension or frequency to produce a standing wave pattern. It is tempting to look only at the amplitude of the wave and...
Page 8: Introductory Activity
WA-9857 Power Supply Part of WA-9857 Elastic Wave Cord (1 meter) Part of WA-9857 (or SE-9409) Clamp or other device for securing the String Vibrator SE-7286 or similar This activity works best with two or more people. 1. Attach the String Vibrator to the table. You’ll be stretching the cord to about 2 m, so leave enough space.
Page 9: Demonstration 1
Banana Patch Cords SE-9750 *The recommended inelastic cord (PASCO part ME-9876) has a linear density of 1.5 g/m. **This demonstration is easier to set up with a Sine Wave Generator (ME-9867), or another ±10 V, 1 A function generator in place of the fixed-frequency power supply, because it allows you to adjust the driving frequency instead of the elastic cord length.
Page 10: Demonstration
String Vibrator String Density and Wavelength 4. Loosen the clamp on the String Vibrator and slide it along the table to adjust the length of the vibrating part of the inelastic cord. Adjust it so that knot connecting the elastic and inelastic cords is at a node.
Page 11: Closed Tube Analogy
Part Number WA-9857 String Vibrator Power Supply Part of WA-9857 Elastic Wave Cord (50 cm) Part of WA-9857 (or SE-9409) Black Thread (50 cm) ME-9875 or similar Clamp or other device for securing the String Vibrator SE-7286 or similar Super Pulley...
Page 12 String Vibrator Closed Tube Analogy 4. Adjust the hanging mass (or the driving frequency) so that there is a node at the blade and an anti-node at the knot connecting the thread and the elastic cord. Demonstration This demonstration is analogous to sound produced by a pipe with one open end and one closed end.
Page 13: Experiment 1: Wave Speed
Part Number String Vibrator WA-9857 Power Supply Part of WA-9857 Elastic Wave Cord (50 cm) Part of WA-9857 (or SE-9409) Universal Table Clamps (qty. 2) ME-9472 or similar 45 cm Rods (qty. 2) ME-8736 or similar Force Sensor CI-6746, CI-6537, or PS-2104...
Page 14 String Vibrator Wave Speed 2. Cut about 1 m of elastic cord. Measure its exact unstretched length. Measure the mass using a balance. Calculate the Unstretched Linear Density (mass/length). (If your balance is not precise enough to measure 1 meter of cord, measure the mass and length of a much longer piece of cord, and use those measurements to calculate the linear density.) 3.
Page 15 Model No. WA-9857 Experiment 1: Wave Speed Wave Speed Calculated from Tension and String Density You can also calculate the wave speed from the tension (F) and the linear density (µ) of the cord with: (eq. 2) -- - µ...
Page 16 String Vibrator Wave Speed 4. Start recording data just before you pluck the string, then immediately stop recording. 5. View the force and voltage data on a graph, and find the elapsed time, ∆t, between the sudden decrease in tension and the change in voltage. 6.
Page 17: Experiment 2
Model No. WA-9857 String Vibrator Experiment 2: Standing Waves In Strings Equipment Required Part Number String Vibrator WA-9857 Power Supply Part of WA-9857 Inelastic Braided String SE-8050 or similar Clamp or other device of securing the String Vibrator SE-7286 or similar...
Page 18 String Vibrator Standing Waves In Strings adjusted to the frequency of the driving vibrator, one vibrational mode will occur at a much greater amplitude than the other modes. For any wave with wavelength λ and frequency f, the speed, v, is v = λ...
Page 19 Model No. WA-9857 Experiment 2: Standing Waves In Strings Procedure 1. Adjust the tension by adding to or subtracting from the hanging mass so that the string vibrates in 2 segments. Adjust the tension further to achieve a “clean” node at the center. Also check the end of the vibrating blade;...
Page 20 String Vibrator Standing Waves In Strings 2. For every value of mass, calculate the tension (including uncertainty) in the string. Tension = F = mg 3. Make a graph of F versus n. Describe in words the shape of the graph. 4.
Page 21: Experiment 1
This experiment calls for simultaneous data collection from a force sensor and a voltage sensor. There are several sensor options available; contact Technical Support, or see the PASCO website and catalog for more information. One convenient combination of equipment (which was used for the sample data below) is: •...
Page 22 String Vibrator Teachers’ Notes–Wave Speed Tension F = 10.4 N Wave Speed Calculated from Wavelength and Frequency Stretched Length = L = 2.343 m Number of segments = 4 λ = 1.172 m f = 60.0 Hz v = λ f = 70.2 m/s Wave Speed Calculated from Tension and String Density The unstretched length measured in this part of the experiment will be less than the unstretched length measured initially because of the knots tied in the ends.
Page 23: Experiment 2
Model No. WA-9857 Experiment 2: Teachers’ Notes–Standing Waves In Strings Be sure to measure from the sudden force change, not the relatively slow variation that may occur before the actual pluck. It may be helpful to repeat the measurement a few times and take the average value.
Page 24 String Vibrator Teachers’ Notes–Standing Waves In Strings Analysis Method 2 F vs. n F vs. 1/ n Slope = 3.74 ± 0.01 N ± 4µf 3.74 0.01 N f = (60.0 ± 0.1) Hz L = (0.987 ± 0.001 m) ±...
Page 25: Safety
Vibrator Instruction Manual is copyrighted Technical Support and all rights reserved. However, permission is granted to non-profit educational For assistance with any PASCO product, institutions for reproduction of any part of contact PASCO at: this manual, providing the reproductions are...