In this experiment designed for use with PASCO Capstone software, study standing waves in a string by varying the driver frequency and keeping the number of segments constant. The String Vibrator is powered by the 850 Universal Interface. Students vary both the the frequency and amplitude.
The unusual approach in this version of the experiment is that the students actually provide the tension in the string by pulling directly on the force sensor. This is particularly instructive because the students get a feel for how the tension must change to vary the number of segments. Rather than hanging more weight over a pulley, the students must pull harder to achieve a smaller number of segments. This helps them remember the relationship between tension and wavelength.
The 850 Universal Interface controls the frequency and amplitude of the sine waves applied to the String Vibrator. As the frequency is gradually increased (in 10 Hz increments), the student pulls on the Force Sensor to adjust the tension for resonance with the string vibrating in two segments.
As each discrete measurement is recorded, a graph of force vs. frequency is created in real-time.
To analyze the data, use PASCO Capstone to create a graph of force vs. the square of the frequency. The slope of the resulting straight line is used (along with the length of the string) to calculate an experimental value for the string’s density.