Re: [Phys-L] A waves question

[curtis osterhoudt <flutzpah@yahoo.com>]

There's a quite good opportunity here to have a student do either or both of:
   (1) a demonstration with a heavy, non-stiff spring (so that one can get good, slow, transverse waves); or,
   (2) a simulation on a computer of two waves destructively interfering.

The option (1) gives one a nice tactile intuition that just because the waves might cancel each other's amplitudes at a certain point in time, the spring still has _momentum_ and energy.
Option (2) of course gives more chances to play with different wave shapes and so on, and one can calculate the medium's _velocities_ at each point (dx/dt at each x), showing that just because there's no displacement, that definitely doesn't mean there's no kinetic energy sloshing around.


 
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"As a species, we are forever sticking our fingers into the electric socket of the Universe to see what'll happen next. It's a trait that'll either save us or kill us, but by god it's what makes us human beings. I'd rather be in the company of people who look at Mars than people who contemplate humanity's navel -- other worlds are better than fluff." ~~Terry Pratchett
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> ________________________________
> From: Peter Schoch <pschoch@nac.net>
> To: Phys-L@Phys-L.org 
> Sent: Friday, June 22, 2012 11:33 AM
> Subject: [Phys-L] A waves question
>
> A fairly inquisitive student came up with the following question, and I thought I'd get the reaction of the list as to the best answer.
>
> The course is "Liberal Arts Physics" -- designed as a survey course for those LA majors that need one semester of a science.  The theme was energy conservation (a bit broad, and I would narrow it a bit next time I do it).
>
> We are discussing waves.  The student asked the following (more or less)
>
> If a wave can transit energy that is proportional to its amplitude squared, and energy can't be created or destroyed, what happens to the energy when two waves destructively interfere?
>
>
> Peter Schoch
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