A study in 1987 examined injuries and mortality rates in cats that had been brought to their hospital following falls ranging from between two and 32 stories.
Overall mortality rates were low, with 90 percent of the cats surviving, a fact that supports many ailurophobics.
However, the study unexpectedly found that the incidence of injuries and death peaked for falls of around seven stories, and then actually decreased for falls from greater heights.
The Nature article presents three main variables that determine injury and mortality rate, the speed reached by the cat, the distance in which said cat is brought to a stop, and the area of cat over which the stopping force is spread.
While concrete streets work in nobody’s favor when it comes to stopping falling items, cats suffer relatively little injury, compared with their owners, because they do indeed reach lower terminal velocities and absorb the shock of stopping so much better.
A falling cat has a higher ratio of surface area to mass than a falling human, and so reaches a terminal velocity of about 65 miles per hour, about half that of humans.
Cats are also able to twist themselves so that the impact is spread over four feet, rather than our two. And as they are more flexible than humans, they can land with flexed limbs and dissipate the impact forces through soft tissue.
To answer the paradoxical increase in survival rates once seven stories have been reached, the authors suggested that an accelerating cat tends to stiffen up, reducing its ability to absorb the impact.
However, once terminal velocity is reached, there is no longer any net force acting on the cat, and so it will relax, increasing both its flexibility and the cross-sectional area over which the impact is dissipated once the cat hits the ground.
When cats land, they bend their legs to absorb the shock as we do at our knees.
Obviously this action will lower their bodies toward the ground, especially their heads, thanks to their having four legs.
Above a certain height, the bending action will bring the chin into contact with the ground and so cats dropped or jumping from great heights will contact the ground with force, shattering their jaw.
Vets quite commonly see jaw injuries in cats, usually as a result of their taking too high a leap from a wall.
The question on the terminal velocity of a cat did remind us of a joke.
Because cats always land on their feet and toast always lands buttered side down, you can construct a perpetual motion machine by simply strapping a slice of buttered toast to a cat’s back.
When the cat is dropped it will remain suspended and revolve indefinitely due to the opposing forces.
The risks to different animals of taking a fall were also laid out in 1927.
Gravity, a mere nuisance to Christian, was a terror to Pope, Pagan, and Despair. To the mouse and any smaller animal it presents practically no dangers.
You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away.
A rat is killed, a man is broken, a horse splashes.
For the resistance presented to movement by the air is proportional to the surface of the moving object. Divide an animal’s length, breadth, and height each by ten; its weight is reduced to a thousandth, but its surface only to a hundredth.
So the resistance to falling in the case of the small animal is relatively ten times greater than the driving force.
An insect, therefore, is not afraid of gravity; it can fall without danger, and can cling to the ceiling with remarkably little trouble.
