PASCO WA-9857, Instruction Manual

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String Vibrator Introductory Activity
8
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Introductory Activity
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.
2. Cut 1 m of elastic cord and attach one end to the vibrating blade.
3. Connect the AC power supply to the String Vibrator.
4. Hold the free end of the cord as shown, and slowly increase the tension by pulling it away
from the String Vibrator.
5. Observe the standing wave patterns that occur as you stretch the cord. Note what happens to
the number of segments as you increase the tension. Does increasing the tension cause the
number of segments to increase or decrease?
6. Adjust the tension until the cord vibrates in 4 segments. Then adjust the tension slightly so
that there is a good node at the blade. Maintain that tension for the rest of the activity.
7. Measure the wavelength. (How is the wavelength related to the length of one segment?)
8. Touch the cord at one of the antinodes (the points of maximum vibration). What happens?
9. Touch the cord at one of the nodes. What happens? How is touching the cord at a node
different from touching it at an antinode?
10. Have a lab partner pinch the cord at the middle node without changing the tension. What
happens to the wavelength?
Equipment Required Part Number
String Vibrator 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