The Study of the Catapult Physics II; Period 8 Kim Jensen and Alexis Cooley Background Information: " Throughout human history, we have tried to create original designs for weapons, which attack an enemy from a great distance. One of the most successful of these weapons was the catapult. Yet, many steps were taken before the catapult was created. F" " The very first catapults were created under the direction of Dionysius the Elder, ruler of the Greek colony of Syracuse, Sicily in 399 BCE. He wanted to give his city a strategic advantage in the upcoming war, so in order to prepare his city, Di" " The catapult was a new weapon for attackers, which made the advantage uneven for defenders during enemy siege (Griess 1986). While the defenders still had the capability to prepare for attack by building great walls, attackers, using catapults, could physically defeat these obstacles. Even during the thirteenth century, after the invention of cannons and mortars, catapults were still utilized on battlefields because they were easy to build on the site and were still capable of doing damage. " " Catapults have evolved vastly since the days of Ancient Greece, but they are still present in the artillery of our modern army. The basic principles of the Greeks’ and Romans’ catapults have been preserved. For example, we have massive steam catapults, which are used to launch aircraft from carriers at sea (Catapults: Weapons, 2002). The major difference between these modern catapults is that they use compressed air rather than gravity, tension, or torsion. The benefit of this device is still present, the catapult provides a fast yet controlled energy source and a right angle for the launch. With a catapult objects can be thrown long distances with amazing accuracy." Problem: " Three properties can be exemplified in the use of a catapult: elasticity, energy, and force. Elasticity is seen in the measure of the stretch of the spring loaded in the catapult. This will demonstrate the accuracy of the delivery of the object being flung. Second, energy is present in the conversion of it from potential into kinetic energy. This could demonstrate and determine the range of the object. Finally, force can be studied and measured in the projectile motion. With our project, we will simply measure the initial velocity of the object as it leaves the throwing arm of the catapult." Related Literature: "Through the Catapults: Weapons of Destruction site, we learned the basic principals and history of the catapult. The site explains the necessity for catapults in medieval warfare but does not thoroughly explain the physics of the catapult. The book by Tho" Hypothesis: " A catapult’s throwing arm has a tail which can be set to different lengths to minimize or maximize the throwing distance. We are going to find out the relationship between the lengths of the tail (the longer the tail, the shorter the throwing arm) and the launch velocity. Our hypothesis is that the shorter the throwing arm, the higher the launch velocity." Procedure: 1 "Laid out three 2 m boards in a triangle, with corners overlapping, and secured them together where they crossed" 2 Secured two boards to the back of the triangle for support of the apparatus 3 Fastened a cross piece to the throwing arm about 1 meter from the bottom 4 Attached small shelves about 1/3 of the distance down the two front arms of the triangle 5 Placed the throwing arm through the hole and rested it on the shelves 6 Adjusted the end of the throwing arm’s length for each launch of the catapult 7 Launched the catapult by hitting the throwing arm with a large board Data: Length of Tail (Inches) Trial 1 Trial 2 Trial 3 19.5 "29'5""" "26'5""" "23'6""" Distance 2.74 sec 1.82 sec 1.98 sec Time 22.5 "10'9""" "7'8""" "6'3""" 1.83 sec 1.77 sec 1.69 sec 16.5 "23'10""" 29' 29' 1.65 sec 1.7 sec 1.7 sec Length of Tail (Inches) 19.5 22.5 16.5 Average Velocity (ft/sec) 12.37 4.634 16.186 Average Velocity (m/s) 3.77 1.41 4.93 Analysis: "The data is inconsistent. For example, for the tail with length 16.5 inches, the first trial went 23’10” in 1.65 seconds. Well the next two trials went about 5 feet farther in only .05 seconds. This data cannot be used to prove the hypothesis either correct or incorrect. The experiment should be repeated and with a different hypothesis." Hypothesis: "A catapult’s throwing arm has a tail which can be set to different lengths to minimize or maximize the throwing distance. We are going to find out the relationship between the lengths of the tail (the longer the tail, the shorter the throwing arm) and the launch distance. Our hypothesis is that the shorter the throwing arm, the farther the launch distance." Data: Length of Tail (Inches) Distance (Inches) Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average 16.5 101 105 103.5 105.5 104.5 103.9 15.5 96 96 89 91.5 89.5 92.4 14.5 75 78.5 70.5 76.5 73.5 74.8 13.5 62 63 61 60 62 61.6 Length of Tail (meters) Distance (Meters) Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average 0.4191 2.5654 2.667 2.6289 2.6797 2.6543 2.63906 0.3937 2.4384 2.4384 2.2606 2.3241 2.2733 2.34696 0.3683 1.905 1.9939 1.7907 1.9431 1.8669 1.90052 0.3429 1.5748 1.6002 1.5494 1.524 1.5748 1.56464 Analysis: "The longest tail (16.5 inches) did have the farthest launch distance of 103.9 inches. And the shortest tail, which measured 13.5 inches, had the shortest launch distance (61.6 inches). The trials are also much more consistent than in the first experiment. The distance of the longest tail varies by only 4.5 inches, as opposed to the almost 5 feet in the first experiment. " Conclusion: "Our first hypothesis was not accepted as correct in this experiment. Our data was too inconsistent to draw any sort of conclusion out of it. Every time that the catapult was launched, there could have been different forces acting on it because of human er" Sources: Building a Catapult. 10/31/02 Catapults: Weapons of Destruction. 10/25/02. < http://pages.emerson.edu/students/Carlo_Lim/catapults/Catapults.htm#Modern> "Gende, Delores. “AP Physics Catapult Project.” 10/30/02 " "Griess, Thomas ed. “Ancient and Medieval Warfare.” The West Point Military History Series." " United States: Avery Penguin Putnam, 1986. " "Pulis, Lee. “Construct-a-Catapult.” Technical Educational Research Centers. United States: " " NSTA Press, 2000."