[Phys-L] Re: World Jump Day

["Folkerts, Timothy J" <FolkertsT@BARTONCCC.EDU>]

John Denker wrote

> It's much more impressive if the jump NON-simultaneously.
>   a) Imagine rows of people, with successive rows jumping at succes=
sive
>    times, phase-matched to the surface-acoustic-wave velocity.  Thi=
s
>    launches a plane wave.  Given N jumpers, the amplitude grows lik=
e N,
>    and the energy grows like N^2.

That doesn't seem physically reasonable.
  The first row adds an energy E
  The second row adds an energy 3E
  The third row adds an energy 5E
  ...

Each row has the same available energy but each row adds more energy =
than the previous row.  With enough rows, the final row would be addi=
ng more energy to the wave than the total energy available (i.e. the =
potential energy of the row at its max height during the jump).

So, does the rule break down at large N?  Or does the energy grow lik=
e N, and the amplitude grow like N^0.5?

Tim F
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