You need to adjust your timestep to the amount of time passed between your steps, in seconds. Or something like that. :) At 13:15 2003-05-13 +0200, you wrote: >Hi, > >If I set dWorldSetGravity (dWorldID, 0, 0, -9.8); >with a timestep of 0.01, >the objects are falling very slowly...(like on the moon). > >Could someone explain me why ??? >This -9.8 means 9.8 m/s/s isn't it ? > >Thanks, > >Charles.