第2届丘成桐中学物理奖（2014）清华大学附属中学 关于气球小车的研究定稿.pdf

关于气球小车的研究 成员：张泽宇 黄泽平 指导教师：罗雷生 学校：北京市海淀区清华大学附属中学 1 Investigation on the model car powered by a balloon Member：Zeyu Zhang and Zeping Huang Adviser: Leisheng Luo School: The High School attached to Tsinghua University 2 摘要 气球小车是一种以气球为唯一动力源的特殊装置，它依靠气球向后喷气而形 成的反冲力前进。本文首先用实时摄像记录的方法从实验上系统研究了气球半径 和喷气口面积对小车运动参数和效率的影响。我们的实验结果表明：气球越大， 小车运动时间越长，运动距离增加，加速时间延长，能达到的最大速度越大，但 效率几乎不受影响；气球喷气口面积越大，小车运动距离越长、最大速度越大、 加速时间越短、效率越高。然后我们利用James -Guth 应力-应变关系和理想气体 分子碰壁数公式对气球小车模型进行了系统地理论分析，推导出了小车运动参数 及效率的表达式，与实验结果定性符合。我们的研究结果对喷气式动力汽车的设 计具有重要的指导意义。 关键词：气球小车、James -Guth 应力应变关系，理想气体分子碰壁数，位移， 效率 3 Abstract The model car abstract powered by a balloon is a vehicle propelled by a recoil force of the ejecting gas from a balloon. In this paper, we experimentally investigated the effects of the balloon size and the jet area on the motion and efficiency of the car. Our experiments show that the running time, distance, acceleration time, and the maximum velocity of the car are increased with the balloon size. However, the balloon size has little effect on the efficiency. With increasing the jet area, the running distance, maximum velocity, and the efficiency are increased, while the acceleration time is decreased. Based on the James-Guth stress-strain relation and the equation concerning the number of the ideal gas molecules colliding with the wall we deduced the expressions for the generated recoil force and the motion parameters of the car. We found that the deduced expressions fitted the experiments very well qualitatively. Our results are helpful for the design of the future jet car. Key