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Name:  Rick B.
Status:  student
Age:  17
Location: N/A
Country: N/A
Date: 2000-2001

My name is Rick Brawley and I am on the High School Science Olympiad team at my High School. And I have a question,actually two. There is an event called Bottle Rockets, and we have been having some trouble with it. The principle is simple, take a two-liter bottle, fill it with only air pressure and water, and make it stay in the air the longest. With the air and water, the air pressure remains constant at 60 p.s.i. so we can only change the water volume. So my first question is How much water do we put in? We've tried several times to get the perfect amount yet we have not succeeded. Second is the size of the parachute. My physics teacher told me that a parachute works by increasing the surface area of an object to the point that the wind resistance is enough to slow the object down. He said that there was a formula that used surface area, and weight to give a terminal velocity. I have been unable to find that formula and was wandering if anyone knew what I was talking about. Any help that I can get on this will be a huge improvement to our guess and check method. Thanks.

With regard to your second question. The physics of realistic parachutes is very complicated, and the subject of numerical computer models. I would suggest you do a web search on "physics of parachutes" or "parachute physics", maybe on But I do not think you are going to find any simple formulas for what happens.

Vince Calder

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