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As part of my project to see how fast rex could have made a change of
direction, I've been trying to calculate the moment of inertia for a 40 foot
long rex about a vertical axis a little forward of the hips. Unfortunately,
I do not have access to detailed metrics on the rex, so I've had to make do
with estimates based on skeletal images. I have tried several approaches
with different source material and the lowest value I have obtained so far
is roughly 700,000 lb. ft.^2. Most (but not all) of the values I've
obtained fall below one million lb. ft.^2. If anyone has access to any of
the following, I could refine this figure further.
-likely width and height of torso on a 40 foot rex at regular intervals from
end to end (preferably a foot or less)
-cross sectional areas at similar regular intervals
-a fore-aft mass distribution curve (can, but need not, include the legs)
Or if anyone has come up with their own estimate of the rex moment of
inertia, I'd love to hear all about it.
By the way, just for comparison, a typical 200 pound man has a moment of
inertia about his vertical axis of about 18 lb. ft.^2 (I've largely
discounted the legs on both the rex and the human). So my estimates suggest
that rex would have required roughly 40 to 50 thousand times as much torque
to similarly alter its rate of rotation.
Well *I* thought it was interesting, but maybe I'm just easily amused.