题目

由于流体具有粘滞性，因而物体在流体中运动要受到流体的阻力．科学家们已测得半径为R的球在流体中以速度v 运动时受流体阻力大小为F=6πηRv，其中η为流体的黏滞系数，不同流体η不同，它由流体的性质决定．某课外兴趣小组在研究性学习活动中为了测定某种流体的黏滞系数，设计如下实验：让密度为ρ=1.2×103 kg/m3半径为R=3cm的实心球在密度为ρ0=0.8×103 kg/m3的透明液体中竖直下落，发现球先加速下落后匀速下落，该兴趣小组的同学用频闪摄影的方法An old man lived in a city in the southwest of the United States. One day he 【1】 his son in New York.“I hate to ruin (v. 破坏) your day, 【2】 I have to tell you that your mother and I are divorcing (divorce v. 离婚),” he said. “Dad, what are you 【3】 about?” the son asked.“We are sick of (厌倦)each 【4】 and I'm sick of talking about this. So you call your sister in Chicago and tell her,” the old man said. The son called his sister in a 【5】, “Mom and dad are getting divorced,” he said. The daughter called her dad right 【6】, “Don't do a single thing until I 【7】 there,” she shouted at him. “I'm calling my 【8】 back and we'll both be there tomorrow.”The old man hung up his phone and 【9】 to his wife. “Okay, they are coming back 【10】 Thanksgiving,” he said. “Now, how do we get them here for Christmas?”