Dear Listers
Perhaps there is someone out there who can relieve me of my morning puzzle. It is stopping my normal activities.
While walking to work, I pass by a train line that carries the coal trains that deliver the largest amount of export coal in the world.
This morning, an empty coal train came to a stop nearby. It then started to move again.
When it stopped, I noticed the usual ripple of sound that accompanies the concatenation of carriages as they shunt into each other.
When it started up again, the auditory ripples were much more pronounced and they repeated in both directions for some time.
What I noticed was that the speed of the ripple event was vastly greater than the speed of travel of the train. That is, the wave event was its own event.
Does anyone know of a technical account of what is going on to account for these speed differences? Does the ripple speed up as it goes down the train? It certainly seems to.
Anyway, I pose my problem in order to free my brain up, a little.
cheers
keith russell
newcastle OZ
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