1) Is some limit of objects affected by physics? I've tried to build wall made of bricks and if wall contain over 90 bricks (about) and if ball strike into wall jME crashes (I dont know why)
2) How to place object exactly at each other? If I build ma wall with exact size (for example first brick start at y-axis 0 and end at 1, second start at 1 and end at 2 etc.) jME crashes too. I must make bricks a little bit smaller, but then they at start they fall down… and if I set its node to rest (node.rest(); ) they are in resta t start, but on first action (crash with ball) they fall down like before, so it is no soluion.
- The number of contact points is limited in ODE (which you are most likely using, if you use jME Physics 2). Have a look at stress- and domino tests for tricks to avoid many contacts (auto disable and rest method). Though imo ODE should not crash in this case, but it does.
- same as 1: too many contact points at the same time. ODE is probably not the right physics engine for your needs. Unfortunately JOODE would not be better. And we don't have any other bindings. I'm not sure about which physics engine would support that, but I guess PhysX would…
Thx, and PhysX is physics engine for java? And where can i get it or some official page, docummentation? I was searching in google and I didnt find useful information 
No, PhysX is C++. But a Java binding was started here. Baune even said he’d make a jME Physics 2 implementation.
Ok thx, i will look at it…
One last question, I need very "primitive" phycics system. I only need to use Boxes… no joints or sometnig like that… maybe no spheres… only "boxes physics"… Is it hard to make own primitive physics based only on boxes colisions? (but many boxes }:-@ )
Making an own simple physics system is not really ‘hard’ (e.g. look at this). The complex stuff are the colliders (box-box in your case) and the joints. Yes, you will need them - contacts between boxes are usually modeled as joints (there are other possibilities though). Joints make it complex as you need sophisticated computational methods to simulate correct behavior of objects touching multiple other objects (or joint in any other way)…