如图所示，在竖直平面内有一半圆形轨道，圆心为O．一小球（可视_爱下问搜题

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问题选择题

如图所示，在竖直平面内有一半圆形轨道，圆心为O．一小球（可视为质点）从与圆心等高的圆形轨道上的A点以速度v₀水平向右抛出，落于圆轨道上的C点．已知OC的连线与OA的夹角为θ，重力加速度为g，则小球从A运动到C的时间为（　　）

A．

2ν0

g

cot

θ

2

B．

ν0

g

tan

θ

2

C．

ν0

g

cot

θ

2

D．

2ν0

gtan

θ

2

答案

由几何关系可知，AC水平方向的夹角为α=

π-θ

2

，根据抛体运动的规律，

知tanα=

y

x

=

1

2

gt2

v0t

=

gt

2v0

则t=

2v0tanα

g

=

2ν0

g

cot

θ

2

．故A正确，B、C、D错误．

故选A．

完形填空

I am my mother’s third child. When I was born, her doctor gently explained to my mother that my left arm was __16__, below the elbow(肘部). Then he gave her some __17__:“Don’t treat her any __18__ from the other girls. Demand more.” And she __19__!
My mother had to work to __20__ our family. There were five girls in our family and we all had to __21__. Once when I was about seven, I came out of the __22__,“Mom, I can’t peel (削……皮) potatoes. I only have one hand. “You get back to peel those potatoes, and don’t ever use that as a(n) __23__ for anything again!” Of course I could peel potatoes with my good hand, while holding them down with my __24__ arm. There was always a __25__ , and Mom knew it, “If you try hard __26__,” she ‘d say, “you can do anything.”
Once in the second grade, our teacher had each of us race across the monkey bars(高低杠). When it was my turn, I __27__ my head. Some kids __28__ . I went home crying. After work the next afternoon, Mom __29__ me back to the school ground. “ Now, __30__ up with your right arm”, she advised. She stood by __31__ I practiced, and she __32__ me when I made progress. I’ll never forget the __33__ time I was crossing the bars. The kids were standing there with their mouths open.
It was the way with everything. When I __34__ I can’t handle things, I see Mom’s smile again. She had the heart to __35__ anything. And she taught me I could, too.

B．differently

A．pay attention

D．explanation

多项选择题

《国家土地管理局、国家工商行政管理局关于对土地价格评估机构进行登记管理有关问题的通知》([1995]国土[籍]字第10号)规定，有( )的土地价格评估机构，可在全国范围内从事土地估价工作。

A．2名以上土地估价师

B．4名以上土地估价师

C．7名以上土地估价师

D．20万元以上注册资金

E．50万元以上注册资金