what is the equation for the acceleration (or decelleration) of two objects after they collide?

collisions don''t change acceleration. if you have something like gavity or wind or whatever, it''ll continue to accelerate.
after colliding, the things that change are direction(not always) and velocity.
for 2 objects:
obj1 - m1,v1
obj2 - m2,v2
the equation is that the inital m1*v1 + m2*v2 will be the same as the final. since mass usually don''t change, v1 + v2 initial should equal v1 + v2 final. this is assuming the objects are perefectly elastic.