RE: G forces, Car Crashes and T. rex

[Sim Koning <simkoning@msn.com>]

Dann Pigdon wrote

> This would seem to assume a straight fall onto the chest. If a tyrannosaur 
> slipped while moving
> quickly, it may have had enough time to tip itself one way or the other and 
> slide along on its side.
> This would avoid undue forces on the front of the chest, prevent a 
> potentially jaw-busting impact,
> and a sliding stop would also help to gradually dissipate the momentum 
> (unlike a Dirty Harry
> style 'sudden impact').
 
 
  I'm not sure if the 14-16 G estimates for the head should even be considered. 
It's not like the a Tyrannosaurus rex's neck would inexplicably go limp during 
the fall. The neck would continue to support the head, so I imagine it would 
only be in free fall for about the same distance as the body. The number of Gs 
for the head should be about the same for the body right? So if the head 
weighed about 360 kgs, then at 6 Gs it should effectively weigh 2160 kgs (4752 
lbs). The question is would a T. rex neck be able support its own weight, plus 
the weight of a 2 tonne head? If the neck wasn't strong enough, then how much 
would the g-forces be reduced due to the gravity resistance of the neck 
muscles? 
 
 I'm not sure what side would have been best for this animal to fall on. If it 
fell on its belly while running, it would run the risk of rolling over its own 
neck, which would not be good. However, the dorsal neck muscles may have been 
the strongest (since they support the neck and head), so a fall in that 
direction may have been the best as long as it fell in an angle that would 
allow it to skid more or less rotationally and sideways as you say. I would 
guess a fall to the side would be the safest overall, since the contact surface 
area would have been the greatest and the neck and head could have been lifted 
well away from the ground. I think when I have time, I'll just draw all this 
out rather than trying to describe it. I'm not a bad artist and my sister's 
fiancee is a pro concept artist and an expert with Photoshop. I'll draw a T. 
rex falling while running, falling sideways, skidding on mud etc. and post the 
links when I'm done.  
 
 
   Another point I think I should make on the g-force tolerance issue, is that 
extrapolating on human g-force tolerance is somewhat fallacious. Comparing the 
durability of a robust 6 tonne killing machine that had a body filled with 
natural "air bags" and a head made to withstand enormous forces exerted on it 
when struggling with prey with mostly soft, squishy and usually out of shape 
humans is questionable at best. What I think it does tell us is that if humans 
can survive 50 to 100 g impacts, then it's probably not a stretch to think that 
giant theropods could survive falls, possibly even without serious injury. This 
makes sense to me, because I have a hard time imagining them as predators 
otherwise, slow or not. Simply slowing them down does not do much to fix the 
problem. As Greg Paul has pointed out, a slow predator would also have highly 
telegraphic attacks, and when you are trying to kill things the size of 
elephants armed with all sorts of nasty weapons, your risk factor goes up. Even 
a T. rex chasing after its prey at 15 to 20 mph would still have to worry about 
its victims falling down in front of it and potentially tripping them up (like 
horses falling in a race) in the process. 
 
 
So I'm hoping I won't see anymore documentaries showing theropods dying because 
they tripped over a log... 
 
 
 
 
Simeon Koning   
 
   
 
 
 
  
 


 
 
 
----------------------------------------
> Date: Mon, 22 Nov 2010 08:42:28 +1100
> From: dannj@alphalink.com.au
> To: dinosaur@usc.edu
> Subject: Re: G forces, Car Crashes and T. rex
>
> On Mon, Nov 22nd, 2010 at 6:07 AM, Sim Koning wrote:
>
> > I've been doing what I can to read up on G forces, the effect they have on 
> > the human body and
> > how that might relate to giant theropods and other dinosaurs. From what I 
> > remember of Farlow's
> > calculation's, a T. rex's torso dropped in a deadfall would impact at about 
> > 6 Gs, while the
> > (765lb?) head would impact at about 14 Gs. The calculations for G forces 
> > during a fall while
> > moving 20 metres per second were 9 Gs for the body and 16 for the head.
>
> This would seem to assume a straight fall onto the chest. If a tyrannosaur 
> slipped while moving
> quickly, it may have had enough time to tip itself one way or the other and 
> slide along on its side.
> This would avoid undue forces on the front of the chest, prevent a 
> potentially jaw-busting impact,
> and a sliding stop would also help to gradually dissipate the momentum 
> (unlike a Dirty Harry
> style 'sudden impact').
>
> Such an 'inglourious' stop might cause the occasional 'basterd' rib though 
> (which I believe aren't
> that uncommon in tyrannosaur skeletons).
>
> --
> _____________________________________________________________
>
> Dann Pigdon
> Spatial Data Analyst Australian Dinosaurs
> Melbourne, Australia http://home.alphalink.com.au/~dannj
> _____________________________________________________________
>