bge grenade

hi, i need a script that simulate the force of grenade .I thought the script of gravity, but instead of attracting, apply a force of repulsion ,but i don’t know how to make it.That force should be apply afther about 6 seconds. Of course, the force must come from the grenade that i launch.

Please,help me:eek:

sorry for bad english

Video tutorial on how to implement explosion physics: http://www.youtube.com/watch?v=KdA7f421QWI#t=51s