摘要
2019年北京理综试卷第24题考查了雨滴下落时受到的空气阻力f。题干中的条件“由于大量分子在各方向运动的几率相等”暗示考生从分子碰撞和分子热运动的角度思考问题。利用传统的分子碰撞模型计算出的空气阻力f∝v,而标准答案则是从流体模型出发证明f∝v^2。这里给出一种修正的分子碰撞模型,从微观上指出空气阻力既包含分子热运动导致的f∝v的部分,也有流体模型导致的f∝v^2的部分。
The No.24 physics question in 2019 Beijing College Entrance Examination asked the students to investigate the air resistance of rain drops.Its statement that“The air molecules move in all directions with equal probability”implied the examinee to solve this question in term of the random thermal motion of air molecular and their collision with rain drops.The traditional collision model shows that the air resistance is proportional to the velocity of rain drops,but the answer employs fluid model and shows air resistance is proportional to the square velocity of rain drops.Here we put forward a modified collision model,which shows microscopically that the air resistance contains two terms,which are proportional to velocity and square velocity of rain drops respectively.
作者
胡继超
陈曦
HU Jichao;CHEN Xi(The High School affiliated to Renming University of China,Beijing 100080)
出处
《物理与工程》
2019年第4期68-72,共5页
Physics and Engineering
基金
北京物理学会2018—2019年度课题“新课改背景下的高中物理教学实践研究”(WLXH1872)的阶段成果
