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Brain Dump on Wave Speed on Guitar strings Problem Redesign

February 4, 2018

For next time around, here’s the problem I’m redesigning for students to work on during no our first day of traveling waves, which comes after various explorations, discussions, exercises, clicker questions. For context, the day only focuses on making different shapes pulses, measuring wave speed on slinkies, and what factors do and don’t effect wave speed. A lot of this will then orient us to following question. How fast do pulses travel along guitar strings when you pluck it?

Each group will be given a loose guitar string sample and the manufacturers recommended tensions. A guitar will be at front of room for examining and measuring, as is a scale and meter sticks.

The subgoal will

Need to be determining the linear mass density of their string, its wavespeed, the echo time on their string of the guitar (pulse to travel down and back once), and finally how many echoes reach the bridge of the guitar in a second (echo frequency).

Students will add their data and calculations to a large table at front whiteboard in the room. They will need to double check at least one other group’s work.

Follow ups:

1. There will be questions to structure our talk about patterns in data. What patterns do you notice? Which strings had fastest moving pulses, why? How does echo time compare across strings? Etc.

2. We will listen to each string using microphone in Logger Pro and compare period for microphone oscillation to predicted echo time- a gentle pluck can be used to keep the higher harmonics subdued. The two should be close to the same –> I can conspire for them to be the same if needed.

3. Follow up questions might ask about how the acts of using tuning peg and fretting change the echo time, but in different ways.

Still needs lots of detailing, but I just needed to get the overall idea down.

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