[aprssig] Our Tornado

[Gregg Wonderly]

On Apr 5, 2012, at 10:33 AM, Dave wrote:

> On 4 Apr 2012 at 12:48, Charles Blackburn wrote:
> 
>> texas yesterday..
>> 
>> what makes it more impressive is that some of those were apparently
>> fully loaded..
>> 
>> charlie
>> 
> 
> From the news footage shown over hear, those "fully loaded" box trailers, 
> when they landed, ended up suprisingly flat, for something that was full.
> 
> Mind you, even an empty one of those weighs in at some 7+ tonne's from 
> memory?  You still wouldn't want one to land on you...
> 
> Empty or otherwise...

surface sq ft * .0027 * windspeed * windspeed == force in pounds of force.

57' * 13.5' = ~670sqft
assume 100mph wind

that presents a force of 20776 pounds or about 10 tons of force, clearly enough to push it across the ground.  Do some trig and you can figure out what the lift force is at a particular "tilt" of the trailer.  It's really easy for 100+ mph winds to lift semi trailers full of stuff, because of the nice flat surface of the trailer.  Lighter objects with less surface area would easily sit still and not move.

http://www.ehow.com/how_5814125_convert-wind-speed-pressure.html

Gregg Wonderly
W5GGW