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Re: T. rex mechanix
Nicholas Wren wrote:
>You can demonstrate this for yourself by doing the Maytag...
>
>While it is true the rex foot was bigger than ours it was still a small
>fraction of the rex's effective body length, and I think this is the
>proportion we need to focus on.
This whole analysis only applies to standing creatures. When running or
even walking, it is easy to turn by stepping slightly differently. If the
force you exert on the ground (and therefore the force the ground exerts on
you) does not act through your centre of mass, you will experience a moment
or torque.
This moment has a component of swaying to one side and a component of
twisting. We usually compensate for the slight twisting which occurs
normally by swinging our arms in antiphase to the ispsolateral legs. T.
rex could not do this, and probably moved its neck to mimimise the effects
on vision.
The important factor in T. rex's manoeuvrability is how far apart its feet
could tread while running. I know the feet would normally have been very
close together, but how far could it have widened the gap without losing
too much speed?
I can briefly spread my feet about half a metre to make a sharp turn. I
would guesstimate (based on distances, moments of inertia and personal
prejudices) that a 12m-long Tyrannosaurus would have to open its legs to
about 4m to turn equally fast.
If I'm on the right track (so to speak), I could work this out a bit more
seriously, with detailed calculations and experiments on running humans.
All the best,
Bill