【正文】 tified parison to be made on the performance of different bats. Thus finally explained why Major League Baseball prohibits “corking” and metal bats. In problem I, taking the COP and the viberational node as two decisive factors of the “sweet zone”, models are developed respectively to study the hitting effect from the angle of energy conversion. Because the different “sweet spots” decided by COP and the viberational node reflect different form of energy conversion, the “spacedistance” concept is introduced and the “Technique for Order Preferenceby Similarity to Ideal Solution (TOPSIS) is used to locate the “sweet zone” step by step. And thus, it is proved that the “sweet spot” is not at the end of the bat from the two angles of specific quantitative relationship of the hitting effects and the inference of energy conversion. In problem II, applying new physical parameters of a corked bat into the model developed in Problem I, the moment of inertia and the BBS of the corked bat and the original wood bat under the same conditions are calculated. The result shows that the corking bat reduces the BBS and the collision performance rather than enhancing the “sweet spot” effect. On the other hand, the corking bat reduces the moment of inertia of the bat, which makes the bat can be controlled easier. By paring the two Team 8038 Page 2 of 20 conflicting impacts prehensively, the conclusion is drawn that the corked bat will be advantageous to the same player in the game, for which Major League Baseball prohibits “corking”. In problem III, adopting the similar method used in Problem II, that is, applying different physical parameters into the model developed in Problem I, calculate the moment of inertia and the BBS of the bats constructed by different material to analyze the impact of the bat material on the hitting effect. The data simulation of metal bats performance and wood bats performance shows that the performance of the metal bat is improved for the moment of inertia is reduced and the BBS is increased. Our model and method successfully explain why Major League Baseball, for the sake of fair petition, prohibits metal bats. In the end, an evaluation of the model developed in this paper is given, listing its advantages s and limitations, and providing suggestions on measuring the performance of a bat. Key words: sweet spot, momentofinertia, CenterofPercussion, BatBall CoefficientofRestitution, BattedBall Speed Team 8038 Page 3 of 20 Contents Summary .......................................................................................................................... 1 Contents ........................................................................................................................... 3 of the Problem .............................................................................................. 4 of the Problem ................................................................................................... 4 Analysis of Problem I............................................................................................. 4 Analysis of Problem II............................................................................................ 5 Analysis of Problem III .......................................................................................... 5 Assumptions and Symbols ...................................................................................... 6 Model Assumptions ............................................................................................... 6 Symbols ............................................................................................................... 6 and Solution..................................................................................................... 6 Modeling and Solution to Problem I......................................................................... 6 Model Preparation........................................................................................ 6 Solutions to the two “sweet spot” regions ........................................................ 8 Optimization Model Based on TOPSIS Method ..............................................11 Verifying the “sweet spot” is not at the end of the bat ..................................... 12 Modeling and Solution to Problem II...................................................................... 13 Model Preparation...................................................................................... 13 Controlling variable method analysis ............................................................ 14 Analysis of corked bat and wood bat [5][6] ...................................................... 15 Reason for prohibiting corking[4] ............................................................... 16 Modeling and Solution to Problem III .................................................................... 17 Analysis of metal bat and wood bat [8][9] ........................................................ 17 Reason for prohibiting the metal bat [4] ......................................................... 18 and Weaknesses of the Model ........................................................................... 19 ............................................................................................................ 19 Weaknesses......................................................................................................... 19 ................................................................................................................... 20