RE: Biomechanics

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Toby White
>
> On Tuesday, September 07, 1999 5:33 AM, John Clavin
> [SMTP:jclavin@microsoft.com] wrote:
>
> [snip]
>
> > This sounds a little far fetched. To start with 20m/s is a too
> quick for a T
> > Rex. It works out at 72km/hr or 45 mph. Perhaps 15m/s is more realistic
> > (about 33-35 mph). Also most buses weigh a lot more that a
> Tyrannosaur. If
> > we assume that our T Rex is about 2 metric tonnes - sprinting
> at 15m/s into
> > a brick wall will have a collision force of about 30 kiloNewtons.
> > If it tripped up and simply fell on the ground, all that force
> would be used
> > up in skidding to a halt on it's chest or side. Lots of
> scrapes, but I can't
> > see it being fatal.
>
> Depends how it landed and what the surface was.  The bus/brick
> wall is the
> upper limit.  Not many brick walls in the Cretaceous.  Then
> again, it probably
> wasn't landing on Nerf, either.
>

Okay, time to whip out the old Holtzian aphorism (aka, please read the
paper!!).

The paper in question is:
Farlow, J.O., M.B. Smith, and J.M. Robinson. 1995.  Body mass, bone
"strength indicator," and cursorial potential of _Tyrannosaurus rex_.  JVP
15: 713-725.

Dr. Farlow posts to the list on occasion, so maybe he can comment more.  In
any case, a bus crashing was NOT NOT NOT NOT the model used for this study:
the calculations employed a number of variables under different
circumstances.

(Incidentally, from their calculations the torso of a 6000 kg _T. rex_
tripping at v = 20 m/s (recognized as unrealistic by the authors, but
previously suggested by certain other workers in the field) under the
Two-Stage Variable Skid Distance model incurs a horizontal decelaration of
5.4 g and a horizontal force of 240,000 N during the first stage, then a
further 0.8 g and 35,500 N frictional force during its 12.4 m skid.)


                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.inform.umd.edu/SCHOLAR/programs/elt.html
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
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