一轻质细绳一端系一质量为m=0.05kg的小球A,另一端挂在光滑水平轴O上,O到

题型:计算题

问题:

一轻质细绳一端系一质量为m=0.05kg的小球A,另一端挂在光滑水平轴O上,O到小球的距离为L=0.1m,小球跟水平面接触,但无相互作用,在球的两侧等距离处分别固定一个光滑的斜面和一个挡板,如图所示,水平距离s=2m。现有一滑块B,质量也为m,从斜面上滑下,与小球发生碰撞,每次碰后,滑块与小球速度均交换,已知滑块与挡板碰撞时不损失机械能,水平面与滑块间的动摩擦因数为μ=0.25,若不计空气阻力,并将滑块和小球都视为质点,g取10m/s2,试问:

(1)若滑块B从斜面某一高度h处滑下与小球第一次碰撞后,使小球恰好在竖直平面内做圆周运动,求此高度h;

(2)若滑块B从h'=5m处下滑与小球碰撞后,小球在竖直平面内做圆周运动,求小球做完整圆周运动的次数。

考点:机械能守恒定律能量转化与守恒定律
题型:计算题
用方框中所给单词的适当形式填空,使短文通顺、正确、连贯。
we, leave, rich, usually, when, enough, remember, with, something, baby
On a snowy evening, a rich lady was standing by the road. She was very worried. Her car had broken down. Just then a poor man, Robert, came. He was on his way back home from work as___1___.
The lady thought, “Is the man going to help me? He looks very cold and hungry.” But to her surprise, he stopped and said __2___ a smile, “What’s wrong, madam?” The lady told him what was happening.
After forty minutes, the car was at last fixed by Robert. The lady wanted to pay him. “No, that’s ___3___, madam.” he said, “I was just helping someone in need. If you really want to pay me back, I hope ___4___ you see someone in trouble, you can give him a hand.” A few minutes later, the lady saw a shabby (破旧的)house by the road. She ___5___ Robert’s words, so she stopped. The hostess(女主人) warmly asked her in. The lady could see that was not a ___6___ family and they needed help. When the hostess was making tea in the kitchen, the lady ___7___ 500 dollars on the table and went away quietly. Robert came home later than before, thinking how hard their life was. Their ___8___ was to be born the next month but there wasn’t ___9___ money. His wife went up to him, gave him a kiss and said softly, “Don’t worry, dear! Everything’s going to be all right. A stranger has helped us out.”
Let’s always be ready to help others because helping others is helping ___10____.
题型:计算题

为促进药物释放,在氨茶碱可可豆脂栓剂中,宜加入少量非离子型表面活性剂,其 HLB值应在

A.11以上

B.10~7之间

C.6~3之间

D.2~0之间

E.0以下

题型:计算题

Mike is kind,determined and full of energy.________,I can’t speak too highly of him.

A.As a result

B.In a word

C.By the way

D.On the contrary

题型:计算题

推孟教授提出正确计算IQ的公式是()

A.IQ=(心理年龄/实际年龄)×100

B.IQ=(实际年龄/心理年龄)×100

C.IQ=(心理年龄×实际年龄)×100

D.IQ=(实际年龄-心理年龄)×100

题型:计算题

“礼仪”定义中的要素不包括()。

A、人际关系

B、专人制定的

C、程序和方式

D、律己敬人

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