Cat Physics
Those looking for a few seconds of entertainment (?) can watch this GIF of the impact of a cat and a soccer ball, and then check out the conservation on the subject between legendary environmentalist Paul Scott (Plug-In-America co-founder) and me.
Paul Scott: I love the physics of this.
Craig Shields: Me too! Conservation of momentum. m1v1 (ball) = m2v2 (ball) + m2v2 (cat).
Paul Scott: Watching the cat’s biomechanics is interesting. As soon as it grabs the ball, it feels for purchase and adjusts its feet. At the time of push off, its tail begins to rotate, providing the rotational force it needs to turn and land on its feet. The kitty over-rotated just a bit, but apparently landed just fine.
Craig Shields: Lands fine, as cats are wont to do. 🙂
As you point out, there is also the conservation of angular momentum, as the cat and the ball start to spin. Neither is spinning going in, but as they fly apart, they seem to have equal and opposite products of mass and rotational velocity.
Speaking of cat physics, here’s something you may enjoy.
We all know that cats land on their feet, and that’s true of whatever height from which they fall above a certain minimum, perhaps a foot; they reorient themselves in a tiny fraction of a second. Cats can survive falling extreme distances, because they instinctively flatten their fairly light bodies out against the wind and achieve a terminal velocity far below that of a falling dog. If a cat falls 80 stories, it has plenty of time to make all this happen, and generally lives through the trauma.
Similarly, they survive falls of up to 3 or 4 stories, not because of slowing by maximizing wind resistance, but because the velocity on impact due to gravitational acceleration isn’t that great.
But falls of intermediate heights (maybe 5 – 30 stories) are usually lethal, as they don’t have time to slow the fall, and the velocity on impact is too great.
