Re: [Phys-L] A waves question

[Andre Adler <andre.adler@gmail.com>]

Here is a short, but nice video on YouTube of oppositely propagating waves and their resultant.

http://www.youtube.com/watch?v=ic73oZoqr70


On Jun 22, 2012, at 4:18 PM, John Clement wrote:

> I would think that looking at standing waves is also in order.  Since the
> energy is proportional to A^2, where does it do when the string is flat?
> But then the string has a velocity so the energy is now kinetic energy which
> is proportional to v^2.
>
> This is are important questions because students have to learn to identify
> where the inergy is located. So some qualitative energy bar charts could be
> profitably used at this point.
>
> But what about a movie of two equal wave pulses of opposite sign crossing
> each other.  There is a point at which there is no amplitude anywhere.  So
> where is the energy???  There are some good wave movies as I recall that you
> can use.  In other words there is no apparent constructive interference.
>
> John M. Clement
> Houston, TX
>
> > Hi,
> >
> > 	I think the "Liberal Arts" level answer is that the
> > energy is at the places of constructive interference.
> >
> > Thanks
> >  Roger Haar
> >
> > =====================================================================
> > On 6/22/2012 10:33 AM, Peter Schoch wrote:
> > > 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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>
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