Hi Ibrahim,
Yes it is possible to design the automobile using CAD software, for example when you use Solid Works, you will need to design each part of the automobile and assemble all the parts like you would in real life to get a finished product.
For simulation, again i will refer to SolidWorks, you will have to define materials that will be used for each part. The engineering parameters(i.e tensile strength,density e.t.c) of the materials you assign to each part will aid with the simulation. SolidWorks uses Finite Element Analysis(FAE) techniques to predict how a part would react to real-world forces, vibration, heat, fluid flow, and other physical effects. So it depends if your computer is power enough to carry out an intensive analysis which would produce more accurate results which will have a smaller deviation compared real world simulation results.
Sorry i used Solidwords, as i am familiar with this CAD software. Am sure any similar CAD software can do the same.
Regards.