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Pressure Wave Simulation: Instructor's Guide

Main Ideas

  • Relationship between voltage and charge
  • Relationship between pressure and displacement waves
  • Reflection and transmission coefficients
  • Sinusoidal functions

Students' Task

Estimated Time: 5 minutes

Students are presented with a picture of molecules at three successive times and asked to draw both the displacement and pressure graph that would represent the picture. A Mathematica simulation of the situation is used to summarize the discussion.

Prerequisite Knowledge

  • Sinusoidal functions.
  • Derivative relationship between pressure and displacement

Props/Equipment

  • Small White Boards
  • Computer with Mathematica

Activity: Introduction

This activity begins with a SWBQ where students are presented with a picture of molecules of molecules at three successive times and asked to draw both the displacement and pressure graph that would represent the picture.wvpressurewavesimtask.jpg

Activity: Student Conversations

  • What are the dots? – there are several analogies to help the students think about what the dots represent:
  • What kind of a wave is this? – answers such as longitudinal and traveling can lead to good conversation.

Activity: Wrap-up

Things to emphasize in the discussion:

  • the connection of displacement, force, and pressure to charge, current, and voltage,
  • the derivative a sinusoidal function is itself a sinusoidal function and also satisfies the wave equation and have reflection and transmission coefficients,
  • the sign difference between the reflection and transmission coefficients for displacement and pressure waves,

Extensions

This is a good follow-up activity to the Creating a Pressure-like wave in a Coaxial Cable kinesthetic activity.

Together, these two activities provide an excellent set up for the Wave Propagation in a Coaxial Cable lab.


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