The physics involved are not the same though are they, for example, as rides get smaller, loops can be much rounder in shape without there being any bad g's. That's just an example to show you that the smaller the ride gets, themore differently forces act on it, if you were to then miniturize the cars as well at the track to such a small size as a K'nex coaster, you can see how the physics are completely different to the way physics are applied to a life size coaster. Ever noticed that it takes like half a second for a car on your K'nex coaster to fall to the bottom of the drop? Where as if that happened on a real coaster, all the occupents would be dead