1.  Open the simulation at:

http://phet.colorado.edu/simulations/sims.php?sim=Wave_on_a_String

Click on the “Run Now!” button. You may want to increase the size of the window.

Start by Wiggling the Wrench. Spend about 5 minutes experimenting with the Tension, Manual/Pulse/Oscillate, Fixed/Loose/No end, and changing the Amplitude, Frequency and Damping. Click on Show Rulers and Timer. Practice moving the rulers around and starting/resetting the timer. Click on the Pause/Play and Step buttons to see how they work.

2.  Set the damping to zero.

3.  Wiggle the wrench to create a single pulse on the top side of the string. Draw your observations of this pulse as it travels to the fixed end and back.

4.  Wiggle the wrench to create a single pulse on the bottom side of the string. Draw your observations of this pulse at it travels to the fixed end and back.

5.  Describe any similarities or differences between the two cases you have just observed.

6.  Reduce the tension and send another pulse. Describe the differences between this pulse and the previous one. Try moving the wrench slowly to improve the appearance of the string.

7.  Change to “loose end” and repeat steps 3 and 4. Draw what you observe for this case.

8.  Compare your observations of the loose end case to the fixed end case.

9.  Change to “no end” and send a pulse down the string. Draw what you observe for this case.

10.  Compare your observations of this case to the “loose end” case.

11.  Summarize your observations:

  1. A wave pulse will flip upside down (invert) when it reflects off of ______.
  1. A wave pulse will not flip upside down (remain upright) when it reflects off of ______.
  1. Changing the tension in the string changes the wave’s ______.

12.  Change to “oscillate” to produce a continuous stream of pulses. Check the “rulers” box and the “timer” box.

  1. Do not change the amplitude or tension settings during this experiment.
  2. Use the ruler to measure the wavelength of your wave (the distance from crest to crest).
  3. Leave the damping setting at zero.
  4. For five different frequencies, measure the wavelength of the wave produced. Record the frequencies and wavelengths in a table below:

Tension setting = ______Amplitude = ______

Trial / Frequency / Wavelength (cm) / Wave Speed (cm/s)
1
2
3
4
5
  1. Wave speed is calculated by multiplying frequency and wavelength. Calculate the wave speed for each pair of frequencies and wavelengths. Record these values in your table.
  2. What is the relationship between frequency and wavelength? Create a graph of wavelength vs. frequency. Find an algebraic relationship (equation) that relates wavelength and frequency. Attach or sketch your graph and its fit equation.
  1. What is the relationship between wave speed and frequency? Create a graph of wave speed vs. frequency. Attach or sketch your graph.
  1. Repeat this experiment for a different string tension. Summarize your results. How does tension affect wave speed? Here you may want to use lower frequencies than with the higher tension used above. Keep the amplitude the same.

Tension setting = ______Amplitude = ______

Trial / Frequency / Wavelength (cm) / Wave Speed (cm/s)
1
2
3
4
5
  1. Repeat this experiment for different amplitudes and the same tension used in part (d) above. Summarize your results. How does amplitude affect wave speed? Keep the frequency the same.

Tension setting = ______Frequency = ______

Trial / Amplitude / Wavelength (cm) / Wave Speed (cm/s)
1
2
3
4
5
  1. What affected the wave speed: frequency, tension, or amplitude?

Lab Report

To complete this activity, each student must turn the following:

·  answers to the questions in this hand out

·  data tables above

·  two graphs:

-  frequency-wavelength graph

-  frequency-wave speed graph

Each graph must have both axes properly labeled, a title, and a best-fit curve or line.