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# RE: Was embedded timber post (80 Tons trailer impact on Structure)

• To: seaint(--nospam--at)seaint.org
• Subject: RE: Was embedded timber post (80 Tons trailer impact on Structure)
• From: "Casey K. Hemmatyar" <khemmatyar(--nospam--at)gmail.com>
• Date: Fri, 23 May 2008 11:27:29 -0700

Bill:

You're right the ft*kips is an Energy unit. However the unit I've indicated is ft-kips (not ft*kips) and it is Force unit.

Regards
Casey K. Hemmatyar, SE

-----Original Message-----
From: William Haynes [mailto:gtg740p(--nospam--at)gmail.com]
Sent: Friday, May 23, 2008 11:07 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Was embedded timber post (80 Tons trailer impact on Structure)

Energy or work has units of ft*kips, not force. The force required to
stop a vehicle also depends on the internal response of the vehicle
during the impact.

On Fri, May 23, 2008 at 1:41 PM, Casey K. Hemmatyar
<khemmatyar(--nospam--at)gmail.com> wrote:
> Great David;
>
> Just to refresh your memory, it  has a 28,340 k-ft of Force but not Energy.
>
> Applying Work-Kinetic Energy Theorem:
>
> Wnet = Kf – Ki= ½*mv^2
>
> W [Work]= ½*mv^2
>
> m=mass; kg
>
> v= Speed; meter/sec
>
> W=(½) (80*1016)*(70*1.609*1000/3600)^2=39,779,275 Joules (This is "Work")
>
>
>
> 1 Joule≈0.73756 ft-lb
>
> F [Force]=39,779,275*0.73756/1000=29,340 ft-k
>
>
>
> Regards
>
> Casey K. Hemmatyar, SE
>
> ___________________________________________________________
>
> From: David Topete [mailto:d.topete73(--nospam--at)gmail.com]
> Sent: Friday, May 23, 2008 8:59 AM
> To: SEAINT
> Subject: Was embedded timber post
>
>
>
> http://news.enquirer.com/apps/pbcs.dll/article?AID=/20080521/NEWS01/805210387
>
>
>
> If my calcs are correct, an 80-ton trailer at 70 mph creates 26,200 ft-kips
> of energy.  (F = 1/2 mv^2 if my math serves me correctly... )  That is about
> 10k at 30".  Or am i way off?
>
> --
> David Topete, SE