[ODE] Little physics problem

[Joao Pereira]

i have a ball and a plane.
i release the ball on the plane and the place is horizontal so the ball 
don't move.
after some time i apply a force (0,10,0) on the ball and the ball starts 
moving. no problem the ball starts gaining velocity has it should.
When i stop applying the force the velocity drop, has it should, but 
after a little time the velocity get stable and don't get down to 0, has 
i studied in physic's it should.
So where is the force that the plane "apply's" that should stop the 
ball???????
How can i model the force applied by the air over my objects??? there 
must also be a resistance there, that i don't see.

Thanks for the answer

João Pereira