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Re: Wave phase reversal on reflection



Herb,

How does the seat of your chair have "the brains or the muscles" to push up
on your fanny and keep you from falling?

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor
----- Original Message -----
From: "Herbert H Gottlieb" <herbgottlieb@JUNO.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, April 25, 2000 10:55 PM
Subject: Re: Wave phase reversal on reflection


On Tue, 25 Apr 2000 22:16:12 -0400 Bob Sciamanda <trebor@VELOCITY.NET>
writes:
Yes, but what is the physical mechanism whereby the cancelling,
reflected wave is generated? Perhaps something like: When an upward
going vertical pulse on a rope encounters a rigid wall termination, the
last rope segment exerts an
upward force on the wall. The wall responds by exerting a downward
pull on
the rope segment (by N3), thus starting a downward going vertical pulse

on the rope.

Bob....

An excellent try ! I really like it!!

The only trouble with the explanation above is that students "know"
that a stupid wall does not have the brains or the muscles to exert
a downward pull ....(unless the wall starts to collapse and fall down
while
the string is attached). Perhaps it might be better to say that the
rigid wall termination provides a reaction that has the "same effect
as a person supplying a downward force on the rope". ......
but I'm sure that someone can provide a much better wording that
I can at the spur of the moment.

Herb
on the