A couple questions

first how do you make something disappear on contact
second how can you make one bject move when another is collided with

…Mostly on the properties that the objects in question contain, because that’s the most common information needed to set the proper sensors right.

In general you will have to use the collision sensor to trigger either the motion, or end object actuators which would ultimately execute actions in the gamespace.

A brief overview of logic bricks, and their inherent functions can be viewed here:
http://download.blender.org/documentation/NaN_docs/BlenderGameReference/logicbricks.html

With the logic bricks you can set the Sensors to Collision, Controllers to and, and the Actuators to visibility and then invisible. For the object to move when touched, set the Sensors to Collision, Controllers to and, and the Actuators to Motion and then under force put whatever you want.

thanks that really helps

you’re welcome. Truthfully, I just figured out how to do that a few days ago :D.