Analytic Essay

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Analytic Essay

Background Essay






Lab Report







Analyzing our Experiment on Water Resistance

Experiments are done and often repeated to gather information. We repeated our experiment three times to discover how shapes affect the speed at which objects move through water. If your experiment is successful, you not only discover what you did the experiment for, but you also understand, and can easily see why the results turned out the way they did. In our experiment we were testing how long it took to pull variously shaped objects through the water. We tested objects with large surface areas and objects which moved swiftly through the water. Our results turned out rather close to what we expected. One could easily obtain the general information and patterns shown in our results. In our hypothesis we predicted the objects with larger surface areas would slow the speed of the train running on the track. In our experiment, our hypothesis proved correct. Our results showed that the most hydrodynamic object with the least amount of surface area, the v-shaped object, put the least amount of tension on the train when traveling through the water. The second most hydrodynamic object, the square with large holes, went the second fastest through the water, and the solid square with no gaps to allow water to pass through, traveled through the water and slowed the train the most. Interestingly enough, we made another unrelated and unexpected discovery. After looking at our analysis of error from our experiment, we found a pattern. We saw that as the hydrodynamic shape of the objects being pulled through the water decreased, the more error there was. This is because, as the surface area of the objects in the water (or really anywhere) increases, the more randomness and "fluttering" there is. This never repeated randomness occurred with the objects with the largest surface areas. The amount of error in the three trials with the most hydrodynamic object had 4.3% less error than the second most hydrodynamic object, and 8.8% less error than the least hydrodynamic object. After discussing this aspect of our project with our teachers, we have found out that this result is not actually random. If thoroughly looked into, this error can be proved to have a pattern. This relates to the theory of Chaos, where anything and everything random has a purpose, and is not actually random. We noticed in our experiment that the more surface area each object had, the more random the path would be when moving through the water. For example, if you drop a piece of paper from twenty feet above the ground, theoretically, the paper will land in a different space each time. This is due to the various ways it moves through the air. If you drop an aerodynamic rock with a small surface area the rock will land in relatively the same place regardless of the wind pattern (unless the winds are abnormally strong). This proves that hydrodynamic objects move through the water in a much more predictable pattern than the objects with a greater surface area. Based on what we learned in our experiment, we assume that the mass of the various objects relates to how the objects move through the water. In our case this did not affect our experiment, for our objects all had the same mass. Overall, our experiment showed that shape has a huge affect on the speed at which objects are pulled through water, partly due to the Chaos Theory. These results greatly relate to scuba diving and other underwater sports. From our results we have learned that the larger or less hydrodynamic an object is, the more water it picks up or the slower it goes. This idea is used in a positive way to propel scuba divers rather than slow them down, in the form of fins. When kicking with a fin on your feet, you will find that you move much faster than you would without it. This is because the fin is longer and wider than your foot, and, therefore, has a larger surface area than your foot, causing more resistance under water. So, when you kick with a fin on it propels the water behind you, pushing you forward. Consequentially, fins take much more energy to kick with. Fins are essential to a scuba diver's speed under water, because with the added bulk and weight you travel much slower. The best fins are obviously the largest ones that cause the least amount of strain on your legs under water. Besides scuba diving, hydrodynamics is also used in swimming, spear-fishing, and boating. In swimming, racers will go as far as shaving every little hair on their body to reduce water resistance. In spear fishing, you never see a spear with a large flat head. This is because the spear needs to shoot through the water at high speeds to spear a fish. To allow the object to go more smoothly through the water, it has a pointed tip. Boats probably use water resistance more than any other water object. Not only does a boat have a pointed bow, but it also has a propeller. The propeller's shape slices through the water and provides the power to propel the boat forward. As the mass of the boat increases, the faster the propellers blades need to move through the water, so a more powerful motor is needed. Our experiment makes the use of water resistance under water easier to understand. As in any experiment, error was present and easily seen in ours. Throughout the process, it became easier and easier to see how the littlest fault could change the results of a whole project. The first account of error in our experiment involved the way we timed our objects by using a stopwatch. Something so little as stopping the time a few tenths of a second late or early could severely change the results. Although in our case the time differential was great enough where detailed timing was not one of the more sufficient error factors. The next hint of error was the inconsistency of the batteries that were pulling the train. As most of us know from experience with batteries, they are not always reliable and sometimes are weakened while running. This also could have thrown off the timing of the experiment, accounting for even more error. The third source or error we traced was the specific way the objects were pulled through the water. Some objects were pulled at an angle and others may have been pulled in a straight line. Others may have been pulled through the water a little bit more sideways and created a not as much water resistance on that object. This may have been the highest contributing factor of error in the entire experiment. Next, we found that even the various currents caused by students kicking in the water could change the path of the object and throw the time off even more. In our experiment we had a stick leading a fishing line into the water. One end of the line was attached to a toy track, and the other end of the line (The part under water) was attached to one of the three objects we were towing. On the stick, the line exerted much of its pull strength into the stick. The paper clip attached to the string sometime was bent or loose, which affected the way the line moved on the string. Consequently, the various depths at which the object was being pulled through the water was altered. After pondering the various accounts of error we concluded that it was not so much one specific problem in our experiment but all of the tenths of a second added together to equal a greater amount of which the timing was incorrect. Improving our experiment has proved to be more difficult than we first suspected. As middle school students we are not expected to use computer generated timing devices to measure the speed of an object moving through water. This has proved to be one of the only semi-realistic ways to greatly reduce most of the error that was created. Also, we believe testing the speed of the objects over and over until we could not possibly bear it any longer would have reduced some of the calculated error. However this was not possible due to the lack of time at the pool. One possible improvement that should have been made to improve the results of the experiment, was to attach the objects to the fishing line in a different way to reduce the "fluttering" of the objects while moving through the water. If the fishing line was attached at more points than just a few, the direction that the object was traveling could be in a more direct path, opposed to an uncontrollable zigzag. We also could have found a way to reduce turbulence in the water during the process of towing the objects. To do this we would have to lower the objects into a completely still pool of water with no one in it. Another problem we had involved the way we pulled the objects. A more consistent and reliable way of pulling the objects, would be to use a motor and a swiveling reel. The motor would rotate the reel and bring in the fishing line at a steadier rate, without the possible loss of energy as was the case with the batteries. Besides what we did wrong, much of our project experiment was done in a well thought out way. Since our experiment is based on the discovery of how shape affects the speed at which objects go through water, we had to make everything besides shape similar between the objects. So, with the string, all of the objects weighed the same, had the same string length, were pulled through the water an equal distance, were in the water an equal amount of time, were made of the same materials, were pulled by the same thing, and were pulled through the same water in the same temperature. From our experiment we learned how precise all calculations must be to produce the targeted results. We learned how greatly the shape and surface area of the objects effects the way and the time it takes to move through the water. We noticed how enormous the time differential was between a hydrodynamic object and an flat object that creates a lot of tension. Although much error was present in our experiment, we feel our experiment was successful enough to give us a general idea on how shape affects the speed at which objects go through water.