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Inquiry: Laws of Strings

Purpose: To determine the frequencies of strings in relation to length, tension and diameter.

When a wire vibrates in a magnetic field, the field induces a voltage in the wire. The signal from this wire can then be displayed on an oscilloscope. The frequency of the signal can then be determined by Lissajou figures. Your data can then be plotted and the relationships for a straight line can be determined.

Procedure:

Tension Experiment: Place the two bridges 0.70 m apart. Use the 0.0356 cm wire. Put 1.0 kg mass on the end of the wire and determine the frequency of wire. Repeat procedure for 1.0 kg increments up to 4.0 kg.

Length Experiment: Place a 3.0 kg mass on the 0.0356 cm wire and determine the frequency of the vibrating wire for the lengths (0.70 m, 0.60 m, 0.50 m and 0.40 m) between the bridges.

Diameter Experiment: Place a 2.0 kg mass on the end of wires of 3 different diameters (0.0356 cm, 0.0510 cm and 0.0600 cm). Be careful to keep the distances between the bridges the same (0.70 m).

Inquiry Questions:

  1. For all three experiments graph frequency versus the dependent variable and then modify the variable and re-graph to prove the linear relationships with an R2 value. Print out your graphs and include them in your notebook.

  2. A string plays a 232 Hz sound when plucked. If the string is cut in half and plucked again what will be the new frequency in Hz?