EridanMan writes:

I read a statistic somewhere that if you touch-down at 50 mph, assuming
a constant 9G deceleration (Easily Survivable), you only need 10 feet
to come to a full stop.

About 9 feet, 4 inches.

Increase to 70mph, and you need 40 something feet.

Nope. More like 18 feet, 4 inches.

The distance varies as the square of the touchdown velocity.

And human beings can survive up to at least 46 Gs if they are properly
supported and braced for impact, with some temporary sequelae. Nine
gravities of acceleration is trivial to survive, but some people will
black out if the acceleration is sustained (almost invariably with no
aftereffects). Aerobatic aircraft can generally withstand more than 9
Gs, and top aerobatic flyers can fly at such accelerations as well.

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