如图所示,半径为R的半球支撑面顶部有一小孔.质量分别为m1和m2的两只小球(视为

题型:计算题

问题:

如图所示,半径为R的半球支撑面顶部有一小孔.质量分别为m1和m2的两只小球(视为质点),通过一根穿过半球顶部小孔的细线相连,不计所有摩擦.请你分析:

(1)m2小球静止在球面上时,其平衡位置与半球面的球心连线跟水平方向的夹角为θ,则m1、m2、θ和R之间应满足什么关系;

(2)若m2小球静止于θ=45°处,现将其沿半球面稍稍向下移动一些,则释放后m2能否回到

原来位置?

      

考点:牛顿第二定律
题型:计算题

招标人的代表和评标专家与()有利害关系的,不得进入评标项目的评标委员会。

A、招标人

B、投标人

C、业主委员会

D、招标项目

题型:计算题

阅读理解。

     Because earthquakes happen without warning, it's important to take steps now to prepare. Because you

don't know where you will be when an earthquake happens, prepare some supplies for your home, workplace,

and car.

    1. Water.

    A person needs at least 1/2 gallon of water daily just for drinking. Store at least 1 gallon of water per person

per day and be prepared for a 72-hour period. It is suggested that you buy bottled water. Keep bottled water

in its original container and do not open it until you need to use it. Also, do check the"use by" date.

    2. Food.

It's always a practical idea to keep a supply of non-perishable(不易腐烂的) food on hand. Have an

enough supply of canned food, powdered milk, dried fruits, non-salted nuts and canned juices for at least 72

hours.

    3. Flashlights (手电筒) and spare batteries.

Keep a flashlight beside your bed, at your place of work, and in your car. Do not use matches or candles after

an earthquake until you are sure that no gas leaks. Prepare a battery-powered radio and spare batteries. Most

telephones will be out of order, so radios will be your best source of information.

    4. Clothes. 

    If you live in a cold place, you must think about warmth. You might not have heat after an earthquake. Think

about your clothing and bedding supplies.

1. Why should people prepare themselves for an earthquake?

A. Because earthquakes can be known before they happen.

B. Because earthquakes take place without warning.

C. Because earthquakes usually take place in the neighborhood.

D. Because it's people's daily work to prepare the earthquakes.

2. About the prepared water, which description is RIGHT?

A. A person should prepare 0.5 gallon of water for one day.

B. You'd better use your own containers to keep water.

C. You'd better open the bottled water when you buy it.

D. You shouldn't open the bottled water until you need it.

3. You should prepare all of the following except ______.

A. powdered milk

B. fresh vegetables

C. dried fruits

D. canned juices

4. According to the article we know that ______.

A. we need to prepare some supplies only at home

B. a telephone is the most important prepared thing

C. flashlights but not matches are first used after earthquakes

D. clothes are used to protect your head

5. If you live in a cold place, you should prepare _______.

A. some warm clothes and bedding supplies

B. some hot water

C. some batteries

D. some flashlights

题型:计算题

纸币发行不是越多越好。[     ]

题型:计算题

某工程队在季梁公园建设过程中承包了一项拆迁工程,原计划每天拆迁1250m2,因为准备工作不足,第一天少拆迁了20%,从第二天开始,不断增加工人,加快了拆迁速度,第三天拆迁了1440m2.如果从第一天之后,每天的拆迁面积比前一天增长的百分数相同,请预测一下该工程队第四天可能要拆迁多少平方米?

题型:计算题

我们是不能够将一个原来静止的物体加速到光速,只能无限接近光速。

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