Date: Wed, 8 Feb 2012 09:10:23 -

Author: ---

Subject: Re: Waves on a heavy chain - What should the wave speed be?

Post:


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Urs,

A long rope may show this effect better than the chain.

But what I'm seeing is more complex than what you describe. The wave =
speeds up and then slows down again as it's moving toward the floor.

Paul

On Feb 8, 2012, at 4:48 AM, Urs Lauterburg wrote:

> Paul,
>=20
> It's the nominal tensile stress in the chain that decreases with less =
weight remaining until the end. So the wave will slow down as it =
approaches the end of the hanging chain. We sometimes show this effect =
with a heavy duty flexible sailer's rope that hangs from a long ladder =
that reaches the auditorium ceiling
>=20
> Regards
>=20
> Urs
>=20
> Urs Lauterburg
> Physics demonstrator
> Physikalisches institut
> University of Bern
> Switzerland
>=20
>=20
> Am 07.02.2012 um 00:20 schrieb Paul Nord:
>=20
>> Here's the video:
>> Waves on a Heavy Chain - YouTube
>>=20
>> Can you explain it?
>>=20
>> There is a curious effect here. You would expect the wave speed on a =
chain to be proportional to the tension. If the end of the chain is =
hanging free the tension will change from a maximum at the top to nearly =
zero at the bottom. You would expect a fast wave speed at the top which =
then slows down as it reaches the bottom.
>>=20
>> Attempting to measure this we observe that the wave seems to speed up =
and slow down a couple of times. The wavelength is compressed as it =
reaches the bottom. And it's possible that there are several waves =
traveling at once. The pileup may produce the effect seen here.
>>=20
>> Another explanation is that the tension changes dramatically as a =
compression wave first jerks the chain up and then drops it again. We're =
observing the transverse wave. Evidence of a compression wave is seen =
only by the position of the free end of the chain.
>>=20
>> Paul
>=20


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Here's =
the video:Waves on a Heavy =
Chain - YouTubeCan you explain =
it?There is a curious effect here. You would expect =
the wave speed on a chain to be proportional to the tension. If the end =
of the chain is hanging free the tension will change from a maximum =
at the top to nearly zero at the bottom. You would expect a fast wave =
speed at the top which then slows down as it reaches the =
bottom.Attempting to measure this we observe that the wave seems =
to speed up and slow down a couple of times. The wavelength =
is compressed as it reaches the bottom. And it's possible that =
there are several waves traveling at once. The pileup may produce the =
effect seen here.Another explanation is that the tension =
changes dramatically as a compression wave first jerks the chain up and =
then drops it again. We're observing the transverse wave. Evidence =
of a compression wave is seen only by the position of the free end of =
the =
chain.Paul<=
br>=

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