Science Buddies: "Ask an Expert"

I built a cannon that uses the pressure from sublimation of dry ice to propel a tennis ball. The cannon was built from PVC pipe, etc., according to advice from Make magazine. The pressure is held in the pressure container using a disc of aluminum foil; when the foil disc bursts, the ball is shot out the barrel. For my experiment, I compared a single layer of foil to a double layer of foil. I measured the pressure that built up in the pressure container, and I measured the distance that the ball went before it landed. I did five trials for each condition.

I wonder what category is best for this project? I was thinking that it might go in Eng: Materials & Bioengineering, because it concerns the material used for the burst disc. Other ideas: Energy & Transportation (since the tennis ball is "transported"). Physics and Astronomy (since the physical forces that propel the ball are important). What category would be best?

Another question: I know that ISEF projects can be judged as Science Projects or as Engineering Projects. <http://student.societyforscience.org/ju ... ef?pid=284> As I understand it, the Science projects involve dependent and independent variables, while the Engineering Projects are meant to solve a practical problem rather than test a variable. Can a project in an Engineering category be judged as a Science project because it tests a variable (burst disc made of a single or double layer of foil)? Or are all Engineering projects juged by how well they solve a practical problem (how to shoot a projectile farthest, using dry ice as a propellant)? Which would be best for this project?

Thanks!

Maybe chemistry, since it is propelled by the change of state from solid carbon dioxide (dry ice) to gas?

Hi LaureenMT,

I responded to your question on your other topic thread.