In article ,
"Vaughn" wrote:

"Joseph Gwinn" wrote in message
...
[snip]

Aerodynamic forces (lift and drag) vary as the square of wind speed, so
going from 120 mph to 150 mph raises the forces by a factor of
(150/120)^2= 1.56 to one.

Thanks, but I did not say that the force doubles for each 10 mph, I said
that damage (measured I suppose in $) doubles.

Fair enough. Damage is probably measured in money.


I have heard this repeated by
meda weather people numerous times, and cannot offer a specific reference. I
can, however, mention two factors at work he

1) At a certain speed the wind starts picking up debris and flinging it against
structures. Lower than that speed and it does not generally happen. This is
why the South Florida building code now requires doors and windows to be
missile resistant (the famous 2 by 4 cannon).

2) Once damage to a structure starts, it tends to multiply quickly. One
breached window can result in the eventual loss of the structure.

I would suspect that the weather people got it from the insurance people
then. But I don't know that I believe it, as the propensity to fly will
also vary with the square of wind speed. If one assumes that flying
objects travel at wind speed (a good assumption for random objects if
they are not too dense, and they cannot go faster), the kinetic energy
of the flying objects also varies as the square of the speed, so
doubling every 10 mph still doesn't seem right.

In mathematical terms, doubling every X mph describes an exponential
law, not a polynomial law, but aerodynamic forces and kinetic energy are
quadratic.

Something else must be going on.

Joe Gwinn