I am planning on animating a Dual action out the front style switchblade mechanism. This is for a assassin's creed style hidden blade remake. I was wondering, is there an animation software that reacts to physics? If I push a certain part, can it push other parts? Or would I have to do that all manually?
Sure there are quite many of these in fact. Many (or nearly all that i have used) of the 3d animation packages can do this. Some 2D packages such as game engines can do this (things such as unity/unreal engine can be used as animation packages also)
Image 1: A quick* push animation done in Maya.
You can also use many of the 3D CAD packages to do this (Creo/Solidworks...). These have more physically accurate models behind them and modelling the shapes is easier. There are also simulation software designed for this like Adams/Simpack.
You can also do this in flash if your not above writing 4 lines of code. Personally i would just do this in mathematica.
Please note: Animating your mechanism by hand takes about 2 minutes setting it up for dynamic simulation takes 5-20 minutes so im not sure its worth doing it with simulation. If you animate by hand you dont need to bother calculating the correct springforces etc (which may or may not be known).
* 2-5 minutes to do and playblast