[ODE] Newbie questions.

[longshot]

1)
dGeomID dCreateBox (dSpaceID space, dReal lx, dReal ly, dReal lz);
What is the initial position of the box?
a) (lx/2,ly/2,lz/2)
b) (0,0,0)


2)
This function crashes my app:
dSpaceRemove (spaceid, gid);
According to the manual the function should work always.
I am sure spaceid and gid are valid, but not sure if gid is in spaceid.


3)
dWorldSetGravity (worldid, 0, 0, -1);
gravity makes my object drop but my object does not increase its drop-speed
over time?


4)
Is there a way to read the velocity of an object?


5)
Is a callback function always needed on collision?