quote the manual:
GameStudio includes a physics subsystem, which allows for realistic motion of models. Currently it supports so-called rigid bodies, meaning that the 3d models will not deform during simulation or upon impact. Because this type of simulation is CPU intensive, the physics subsystem is disabled by default. When you wish to use it, you have to register physical entities and then enable them for simulation. This means you delegate exclusive motion control of these objects to GameStudio, as described below. When you no longer need a physical entity, you should unregister it or disable the physics system. While it may be tempting to simply register every object in your game as a physical entity we strongly advice against it because of performance reasons and stability. Whenever motion is simulated using physical approximations there is a risk of "explosions"; basically this means that your objects will do unexpected things such as falling through floors flying off at full speed or other nasty things. Reasonable effort has been put into the physics subsystem to prevent these explosions but with current technology a 100% failsafe method is not feasible. Despite all of these warnings simulated physics is a great way to spice up your game by allowing the player to immerse himself into this artificial environment doing new and unexpected things.

whith commerical version you can only have one phy. with pro you are not limited.there are demo's of the phy. on the download page with the car demo.