aluminum foil and shape???

[corissam76]

My daughter did a project and needs her conclusion. She took 1"X1" pieces of aluminum foil and folded them into different shapes. She folded one in half, one into a triangle, one into a smaller square (by folding it in half then in half again,) the last was rolled into a cylinder. She used the same object to launch these 4 objects so all variables remained the same aside of the shape of the object. The cylinder was launched the furtherst and I need an answer as to why this is so?? Please help!

[kgudger]

Hello and welcome to the forums:

To understand this project better we would need a lot more information. Good job on controlling as many variables as possible! First, that was very good to make sure the mass of each object is the same. What do you mean by "She used the same object to launch"? The method of the launch could play an important role in why the various shapes went different distances.

My first thought is that air resistance plays a big role in this experiment. When launched, how did the objects travel through the air? Did some tumble and others not? Can you videotape (even a cell phone camera) the flights and then look at them in slow motion? This is how I would start to understand this problem.

Keith

[deleted-103788]

If the cylinder is traveling with it's wall surface leading into the flight trajectory, the cylindrical (flying) shape takes advantage of a special case of the Bernoulli Principle, called the "Magnus Effect". It's also sometimes called the Robins Effect after the engineer that researched the effect as it applied to globe-shaped munitions.

You can see this effect in many sports such as a slicing golf ball, a curving baseball pitch, and a quickly-dropping tennis ball with a lot of topspin.

Most round objects develop a spin when thrown. As the thin layer of air (or any fluid actually) on the object interacts with the general environment, a slight but noticeable pressure difference is created. There is slightly less fluidic pressure in the direction of the lead surface's rotation which then creates or dimishes lift depending on how the object is rotating in flight.

[rmarz]

corrisam76 - I believe there are can be an large number of variables at work here, but for simplicity, let's reduce the problem to it's simplest form. Think Occam's razor. One of the experts suggested that wind resistance is likely a main contributor, but there are other variables involved. I agree with that. The form factors present several different surface areas that are presented to the surrounding air. If your launch system were simply gravity, and you just dropped the samples you could probably expect that they would fall to the ground in the same order you achieved in your experiment. The first one to hit the ground likely achieved the greatest launch distance Each one would probably have some part of Bernoulli's principle at work during portions of flight, but probably they are all fluttering or turning in the air. You would need a few hours on a powerful supercomputer to analyze or simulate each of these. The simple answer, unless one of the samples was formed to specifically be an efficient airfoil (like a folded glider that assumed a distinct position in the airstream, or relative wind as they would describe it in aviation terms) is reduced to wind resistance. The smaller the surface area, the more likely it is to fall fastest or be launched farther. Hope this helps.

Rick Marz