如图所示，一个半径R为0.6 m的光滑半圆细环竖直放置并固定在水平桌面上，O为圆

发布时间：2017-08-07 02:27 │ 来源：www.tikuol.com

题型：计算题

问题：

如图所示，一个半径R为0.6 m的光滑半圆细环竖直放置并固定在水平桌面上，O为圆心，A为半圆环左边最低点，C为半圆环最高点。环上套有一个质量为1 kg的小球甲，甲可以沿着细环轨道在竖直平面内做圆周运动，在水平桌面上方固定了B、D两个定滑轮，定滑轮的大小不计，与半圆环在同一竖直平面内，它们距离桌面的高度均为h=0.8米，滑轮B恰好在O点的正上方。现通过两个定滑轮用一根不可以伸长的细线将甲与一个质量为2 kg的物体乙连在一起。一开始，用手托住乙，使小球甲处于A点，细线伸直，当乙由静止释放后。（g取10m/s²）

（1）甲运动到C点时的速度大小是多少？

（2）甲、乙速度相等时，它们的速度大小是多少？

完形填空。
Look at this picture. It is __1__ nice classroom. In the picture, you can see a teacher's __2__ on his desk. It's a Chinese book. Eight desks and eight chairs in the room. You can see a girl and __3__ boys. The girl's __4__ is Julia. She is eleven. The boy __5__a black hat is Tom. The other boy is Tony. They __6__ the same coats and they are the same age. I __7__ they are twins. Tom is a __8__ boy. A book is in his hand. You __9__ see the teacher. __10__ is the teacher? He is taking the photo.
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