I want to simulat a Ak47 projectile movment.the mass=48.19g and speed=830m/s.which commands and parameters is better for use?
Please help.what must i do exactly.it is urgent.
I'm not really sure what you mean by 'realistic', if you mean it should penetrate/deflect off objects that could be quite involved, however firing the projectile should be trivial.
If you're using a RigidBody for the projectile you can just set the velocity. If your game object has no RigidBody you will need to update the position each frame.
There is a question relating to simulating air resistance here: http://answers.unity3d.com/questions/11677/basic-aerodynamics-questions