I'm a c++ and opengl programmer, I'm looking for a physic engine to handle car physic for my F1-like game, I found on youtube some great example of car physic made with Unity3D, but I don't know if the engine can keep the physic real at very high speed like 300Km/h. Thanks you all!
This is a very generic question, which I'll answer with a very generic "yes" :)
More specifically, it depends on what you want. Do you want precise simulation physics, or more arcade like, "fun to play" physics. For either case, there are several samples out there. I advice checking out these:
Unity Car Tutorial: Contains both an arcade, and a separate simulation physics model.
A thread on the unity forum about a collaborative effort of making a car physics engine for unity, very interesting read with lots of pointers.
I recently made an F1 game, and while it certainly doesn't fall into the "Simulation" category of games, it does approximate driving a car at F1 speeds fairly successfully, using Unity's physics engine. It's called Hometown GP.
To achieve this I spent a long time adjusting things like the suspension and downforce to prevent it from rolling or sliding too much when turning.
Unity's physics engine does not simulate aerodynamics, so an object moving very fast along the ground with no suspension will roll or fly off the ground very easily - to simulate the downforce generated by the car's body shape, you have to manually apply downforce via code.
It's important to get the suspension right because it is responsible for maintaining the wheel's contact with the ground as much as possible, meaning the user doesn't lose control because of small bumps.