Materials Needed for each lab group:
target (I use a mad scientist rubber ducky.)
two meter stick (a meter stick that is 2 m long) or two one meter sticks
Students are not allowed to use any other equipment for the challenge and are able to achieve excellent results. This style of gun is very consistent in its behavior. I find that the spring retains a very constant spring constant even after many many uses by students. I specifically do not allow students to use a force scale as that will make the challenge too simple, and removing and replacing the spring in the gun does damage the spring a bit if not done carefully.