Cheetahs are pretty danged fast, but a cheetah only has access to its top speed of 75 mph for roughly a quarter of a mile or so, then it has to decelerate. On average, a cheetah can really only run about 40 mph for any length of time, and even then it needs to catch its prey pretty quickly or risk running out of fuel.
T-Rex was, scientifically-speaking, way bigger than a cheetah. And according to a recent study published in the Journal of Experimental Biology, bigger animals are not the fastest. In fact it’s the medium-sized animals, like the cheetah, that rule when it comes to achieving top speeds. So a cheetah, if it was the animal chasing our heroes in the first installment of Jurassic Park, might have been able to keep up with that Jeep for a few beats, but it would have pretty quickly fallen behind. A T-Rex wouldn’t have stood a chance — in fact, scientists now think T-Rex’s legs were too long compared to the rest of its body for it to be capable of running at all. If it tried, its legs might have snapped under the weight of its portly form. Instead, it probably walked everywhere, though granted it was a really, really fast walker, reaching a top speed of around 25 mph. Fast enough to catch a human on foot, but not fast enough by far to keep pace with a Jeep, even for a few seconds.