On the morning of March 25th nurse Brittney Kirk left her window cracked
open to let in the morning air unknown to her her cat decided she wanted some
of that air to crawled out the window and took a nineteen story plunged to her
death wait scratch that knocked to her death not even to the morgue or to the
hospital the cat survived with only a bruised chest but how did a cat manage
to survive a 200-foot fall when most fifty foot falls are lethal for humans
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saying a cat has nine lives is believed to originate from a cat's ability to
seemingly always land on its feet and survive even the greatest of Falls the
saying is so old Shakespeare included it in Romeo and
Juliet and it even makes an appearance in an ancient Roman proverb but where do
cats extraordinary abilities come from well it's a mix of physics and biology
if the earth had no atmosphere and you jumped off a spaceship you would keep
accelerating towards the ground until you slammed straight into him but in the
real world worse atmosphere acts as a cushion slowing you down as you
accelerate through the sky the air gets progressively harder to push out of the
way at a certain point the force of the air pushing up on you
cancels out the force of gravity pulling you down you're still falling but now
you're no longer speeding out this is called terminal velocity and it's the
fastest an object can fall through the atmosphere terminal velocity isn't the
same for everything it's proportional to the square root of mass over the
downward facing surface area what's important to understanding a cat's
ability to fall is understanding that an object's mass and surface area don't
scale linearly to visualize this let's take a cube with side lengths of one all
these units are gonna be arbitrary it's only the comparison between them that's
important let's say this cube has a weight of 1 now let's make the downward
facing surface area four times bigger well you might have noticed is that now
the mass isn't four times bigger but eight make the cube even bigger and now
it has a downward facing surface area of nine and a mass of 27 the mass pulling
the cube down gets big much faster than the surface areas
ability to slow the cube from drag through the air as a result
generally speaking the bigger the object the higher its terminal velocity or its
max falling speed will be a blue whale would max out falling through the sky at
3,000 meters per second an African elephant eighty meters per second and a
human fifty-five but the average house cat weighing only about eight pounds
comes in at only 26 meters per second this means that after about six storeys
a cat stops accelerating so whether a cat falls off a six story building or a
600 story building there isn't much of a difference so on the physics side a cat
just can't fall very fast but there's also a biological reason behind cats
mysterious abilities cats possessed what's called an aerial right inning
reflex the physics behind this is explained really well in this video by
box which brings us back to the cat it seems to be able to write itself by
flipping in the air without pushing off anything first which would contradict
the law of conservation of angular momentum sounds scary but stick with me
here one of Newton's laws of motion says that something in motion can't just stop
itself unless an opposing force acts upon it basically you can't just change
direction midair Wiley coyote stop but to the naked eye it looks like a cat can
most people assume the cat was cheating by kicking off the hands of the person
dropping it but morees film showed what's actually
happening the first few frames proved right away that the cat doesn't start
its rotation from a kick but what it does do is arch its back and by arching
its back it's divided its body into a front part in the back part the two
parts can work independently you know how a figure skater pulls their arms in
to rotate faster that's what's happening here too early in the rotation the cat
pulls its front legs in and leaves the back splayed out so the front half can
rotate quickly while the back half stays relatively still then halfway through it
does the opposite front legs stretched out back ones tucked in to flip the
other half of its body around and you notice by the time the cat is landing
all four legs are stretched out as far as they can be which means slow rotation
so the cat has rotated itself but not over all the two halves are working
in opposite ways it uses the inertia of its own bodyweight to spin each side and
because the two spins operate separately in opposing directions they cancel each
other out so Newton's law isn't broken and on top of that on long Falls cats
also spread their legs out nearly perpendicular to the ground creating a
sort of parachute against their stomach further slowing their descent and when
they land cat's legs are very springy and muscular and basically act as shock
absorbers their springy legs reduce the force on their bodies and help them
avoid breaking any bones so a cat's ability to survive these crazy high
falls is one part physics and a few parts biology I hope you enjoyed getting
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and remember there's always more to learn