using the physics engine
phent_settype(me, PH_RIGID, PH_SPHERE); //what kind of entity?
phent_setmass(me, 5, PH_SPHERE);
phent_setfriction(me, 100);
phent_setdamping(me, 40,40);
phent_setelasticity(me, 10, 10); //set elasticity
put this in the action for your entity. it sets all the physics stuff and of course you can play with the values.
then in your main function put
"ph_setgravity(vector(0,0,-380));"
should be good.