The egg wouldn't break in that example though. What it would do is travel through the air at a distance relative to the speed of the car and gradually lose height until it smashes into the ground. So no it isnt the air, nor friction, nor turbulence but the force. The egg will not break if it is not released though as alluded to in the post above but then a human cannot exert that kind of force, i am not saying that a mechanical device wouldnt break an egg without releasing it because i really dont know. Bear in mind, in the initial example it is mainly the force breaking the egg because the shell cannot handle the force acting upon it. I am satisfied with the main component being force but if you want to add in terms like pressure and friction that is fine. Goes without saying less force\speed less friction but once and if the egg survives a certain threshold it is in the clear and will not break. Seems to me an egg has more of a chance in water, being fired at the same force than it does in air. For example, the egg is already submerged while fired it survives the same force applied to it while submerged but if the egg is fired\thrown and has to break the surface of the water then it will break at the surface.