Before the advent of microcomputer‐based labware (MBL), “time‐of‐flight” measurements1,2 for the speed of a transverse pulse on a string required elegant apparatus. This paper describes how to use an off‐the‐shelf MBL force sensor and a computer to perform the measurement. The data shown in this paper were collected using Vernier Software's wireless dynamics sensor system and Logger Pro software,3 but almost any common force sensor coupled with a computer or graphing calculator should work. You will also need about 2 m of string or elastic cord4 and a meterstick or tape measure.

Topics
Equipment and apparatus, Sensors, Microcomputers
1.
D.
Kirwan
 and
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Direct measurement of transverse wave speed on a stretched string
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3.
Visit www.vernier.com for details on these products or www.pasco.com for a description of one competitor's products.
4.
We used Cenco's elastic wave cord (http://cencophysics.com/elasticwavecord50feet.aspx), so that the tension could be easily controlled to study the effect of tension on pulse speed. Ordinary string also produces good force‐time data.
5.
In Logger Pro, we collected data at 1000 points/s (the maximum possible for the force probe) for 1 s. Triggering was enabled, with the triggering threshold set at 0.5 N, which worked well with the Cenco elastic wave cord we used.
6.
In Logger Pro, the direction of the pluck is away from the probe for positive values of trigger threshold. Logger Pro's default settings record positive values of force for pulls on the probe's hook. The location of the pluck has little effect on the quality of the data, but does affect the amount of time between the first and second peaks.
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© 2010 American Association of Physics Teachers.
2010
American Association of Physics Teachers
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