Blender 2.78 Hair particles not reacting to force fields

I am trying make a scene with grass moving because of some force fields(attachment). Every time I try to play the animation, the grass moves only for the first 20 seconds and then stops moving at all. I’ve tried changing the strength of the force fields as well but it produced the same result.

Thanks in advance.

Lower Hair Dynamic settings for Stiffness and Damping (ie. 0.1)

PS
The units you mention aren’t Seconds but Frames :wink: