jacimino

I am in the 6th grade and working on an experiment involving parachutes. I constructed 4 small p-chutes;round, square, rectangle & triangle all w/same surface area. I have some basic ?s 1. What shapes are best and why? 2. How close to the ground can you fall and have the p-chute work 3. How often do they fail to open? 4. Do the dif. Branches of the Armed Forces use dif stlyes? 5. How much smaller is the back-up p-chute than the main p-chute? Thank you, James