[ODE] air friction

[Ivan Bolcina]

Actually I have a question on this to.
If you want to simulate drag of friction, than you put some force. The 
problem is, the force will work fore some ammount of time, giving the 
object certain  amount of dV.
The problem is,that by doing this, the object never stops (or it stops, 
but only because float numbers have limited range).  This is also true 
for air friction, I think.
The object in realitiy would never completly stop, since friction force 
would alwasy produce smaller dV for current velocity. But this would 
only be true, if we could operate with smaller and smaller dt.  If we 
operate with fixed dt, I am not sure the results are accurate.

The sistem doesn't seem stable. During some point, the ODE should decide 
that object is moving so slowly, that it is actually stoped.
BTW, friction and drag are actually sum of forces of molecules hitting 
the object, or some other micro events, and we have to simulate this in 
one way or another. The question is how?


DjArcas wrote:

>Uhm, you could read the FAQ.
>
>Q How do I stop things from rolling off into infinity, or pendulums from
>swinging forever?
>A ODE models a universe with frictionless hinges and no rolling friction, so
>problems like those are fairly common. The solution is to apply a force to
>simulate RollingFrictionOrAerodynamicDrag.
>
>http://q12.org/cgi-bin/wiki.pl?RollingFrictionOrAerodynamicDrag
>
>
>----- Original Message ----- 
>From: <barbara.yersin at urbanet.ch>
>To: <ode at q12.org>
>Sent: Wednesday, April 21, 2004 10:58 AM
>Subject: [ODE] air friction
>
>
>  
>
>>Hi guys!
>>I now have a ball  on which I apply a force once (only once => no
>>    
>>
>acceleration, constant speed)
>  
>
>>Then the ball starts rolling, but it never stops. How can I create the air
>>    
>>
>friction effect? How can I stop the ball ?
>  
>
>>Thanks!
>>
>>Barbara
>>
>>_______________________________________________
>>ODE mailing list
>>ODE at q12.org
>>http://q12.org/mailman/listinfo/ode
>>
>>    
>>
>_______________________________________________
>ODE mailing list
>ODE at q12.org
>http://q12.org/mailman/listinfo/ode
>
>  
>