Jurassic Park got it wrong. The scene where T-Rex is chasing the jeep just couldn't have happened, because the animal just isn't that fast and the jeep would easily have been able to get away. I'm Bill Sellers, and I'm a Professor in Natural Sciences at the University of Manchester.
And I've been studying how Tyrannosaurus Rex could have moved. The most important conclusion that we found is that T-Rex was almost certainly unable to actually run. What we did was created a 3D computer model of the skeleton. We put the muscles on, and with the muscles alone, you get quite a respectable sort of 30 kilometer an hour top speed.
But if you do that, you'd find out that actually the legs would shatter under the forces. And in fact, the animal wasn't able to go faster than a brisk walk. Obviously if it is slow, it can't be a pursuit predator. Your options then are either go after other fairly slow moving prey.
The other idea is that actually T-Rex didn't actively hunt at all and was just a scavenger.