Ves On A String Virtual Lab Summary

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ves on a String Virtual Lab

Google PHET and navigate to the waves in a string simulation. Or type in the following web site. http://phet.colorado.edu/simulations/sims.php?sim=Wave_on_a_String Click on Run Now. Adjust the settings on the simulation for zero damping, high tension, manual operation & no end. Wiggle the left end up and down by moving the mouse vertically one time returning to the rest position.
1. Describe the wave.
The waves was a pulse, not a periodic wave. The pulse appeared as a hump that travels along the length of the string and disappeared from the window.

2. How do the individual particles move compared to the motion of the pulse? Watch a green particle.
The energy of the pulse was propagated along the string and
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Change the amplitude to 0.75cm and change frequency back to 1.50Hz. Pause the wave again. Does this change the distance between crests? Is the overall wavelength the same as before?
Increasing the amplitude from 0.50 cm to 0.75 cm does not change the distance between the crests and therefore does not change the overall wavelength.
10. Next, adjust tension one notch down. Does this affect amplitude?____ Does this affect wavelength?_____ Decreasing the tension from high to the next notch in between high and low did not change the amplitude of the wave, but did decrease the wavelength.
11. As tension goes down, what happens to the wavelength?______
As the tension goes down, the wavelength decreased from 4.2 cm to 2.5 cm.
12. Change to pulse, fixed end with zero dampening and high tension. Send a pulse and observe what happens to the reflected wave. Sketch the pulse shape before and after the reflection with the fixed end.

13. Next, adjust tension back to high, change it to a fixed end, pulse, and reset the wave. Send a pulse and when it has traveled about half way to the end send a second. When the first pulse is on its way back and the second is moving toward it pause the simulation and then step it while you observe the
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Reset the wave to oscillate, adjust amplitude to 100, change frequency to 30 and change dampening to 30. What happens to the wave?

What do you think dampening means in terms of energy?
With the dampening, the amplitude of the wave decreases as the wave propagates along the x-axis, but the wavelength appears to be about the same. The dampening must be causing a decrease in velocity because energy is mechanical = 1/2mv2 and velocity = Asin (ὠt). As energy decreases, so will amplitude. Decrease in energy can be caused by friction.

Conclusion:
The objective of this simulation was to create waves on a string by varying the amplitude and frequency of the oscillator and to compare the effect of string tension, dampening, and how the string is held at the end. If the string had no end, then the wave would propagate down the string toward infinity. If the string was held with a loose end, the wave would be reflected back at the oscillator or a fixed end, the wave would be inverted. When a reflected wave would combine with other waves coming from the opposite direction, the wave amplitudes of the waves are summed constructively (amplitudes of the waves are summed) or destructively (amplitudes of the waves cancel out each other). However, in reality the waves are actually moving pass one other and emerge as their original form. These reflected waves will continue forever as long as no force lowers their energy. Adding a damping force decreases the energy of the wave, which caused

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