Help me with my thesis - Biggest problems in implem. physics

Full topic: Help me with my master's thesis - The biggest pittfalls in implementing physics to your game?

Hi, I'm doing my master's thesis(or "Pro Gradu") in the Department of Information Processing Science in the University of Oulu, Finland, and I need some empirical data... and it seems data gathered from forums is valid for this kind of research... SO YOU CAN HELP! (plz do) .. Any answers will be processed anonymously.


So, my first question is:

What are the biggest pittfalls/problems you have run into when implementing physics into your game(s)? (let's say the 10 biggest problems per person, though even one is appreciated


And the second question:

What is your recommended solution to these problems? (if you have any)


Clarification: I need YOUR problems (and possible solutions to them) to present them in my thesis.


Thanks in beforehand to any who have time to answer my silly questions

Problems:
1) synchronizing physics over a network
2) make the player move like you want, though let him behave according to physical laws
3) implementing ragdolls
4) keep objects from intersecting each other or get stuck
5) make the objects feel real

solutions:
1) dont have any
2) dont have any
3) change properties and test carefully, trace bugs (OgreOde specific)
4) shrink the scene (ode specific), change object properties
5) carefully test, change parameters, repeat