His Excellency talks about the “dead-cat bounce”, noting that cats will bounce on the street after falling from a ten-story window even though they have been killed by the fall. One of the many charming lessons of physics, however, is that cats often survive falls of more than seven stories, while they are frequently killed when they fall from between 2 and 7 stories. This is called Hi-Rise Syndrome or the “cat-righting reflex”. What explains this phenomenon? Terminal velocity. Bodies do not accelerate indefinitely. Drag and other factors such as shape, (but not weight, funnily enough) give objects what is a called a terminal velocity: a top speed at which they fall without accelerating further. Everything (on Earth) accelerates at 9.8 meters per second initially (the force of gravity), but at some point the acceleration tops out. If I jumped out of an airplane, my maximum rate of descent might be 56 meters per second. A drop of water tossed out the same plane might top out at a speed of about 8 meters per second. When a cat initially falls from a window, it reacts to the sensation of acceleration by balling up. That’s bad for the cat. Cats that hit the street in a ball don’t do so well. But when the cat reaches its terminal velocity around the sixth or seventh story of the fall, it can no longer sense the feeling of “falling.” So it relaxes and turns around in midair, a move which creates more drag and lowers the cat’s rate of descent. This sensation causes the cat to instinctively spread its legs and brace for impact, which its joints are well-designed to handle. Because of terminal velocity, cats have survived falls from as high as 46 stories. Now back to your regularly scheduled program.
