why are cheetahs so fast?

Answer 1

Cheetahs are simply built different than the other cats. There are three things about their bodies that give them such a speed advantage. First and foremost is their spinal column is extremely flexible or "supple" - much more so than the other cats, or most any other mammals for that matter. The second and third things are the lenghths of their bodies and legs - they are quite long for an animal of that size.

These three things combine to allow the cheetah to have an enormous STRIDE. Watch a cheetah run in slow motion (if you can find a video clip): each stride starts out with the hind feet a good distance in front of the head, the backbone bent almost double, and the front legs streched out behind the animal. The stride ends with the back feet streched straight back and the front feet streched out straight in front of the nose. Now, there is no fundamental difference in the mechanics of the stride between cats, but since cheetahs have the three advantages I mentioned above, the length of each stride (or in other words the distance covered each time the back feet hit the ground) is much longer. That is why cheetahs are so much faster than the other cats.

Answer 2

Cos they are built for speed.