问题 单项选择题

机械泵运转过程中的最高温度不允许超过()℃。

A.80

B.60

C.40

答案

参考答案:A

问答题

在“验证机械能守恒定律”实验中,

I.第一组同学用打点计时器按照图1所示装置进行实验,则

(1)对于自由下落的重物,下述选择的条件哪种更为有利?______

A.只要足够重就可以.

B.只要体积足够小就可以.

C.既要足够重,又要体积非常小.

D.因为不需要知道动能和势能的具体数值,不需要测量重物的质量,所以对重物可任意选择.

(2)已知打点计时器所用电源的频率为50Hz.查得当地的重力加速度g=9.80m/s2,测得所用的重物的质量为1.00kg.实验中得到一条点迹清晰的纸带,如图2所示,把第一个点记作O,在纸带上另取连续4个点A、B、C、D作为测量的点,经测量知道A、B、C、D各点到O点的距离分别为62.99cm、70.18cm、77.76cm、85.73cm.根据以上数据,可知重物由O点运动到C点,重力势能减少量等于______J,动能的增加量等于______J.(取3位有效数字)

II.第二组同学利用图3所示的实验装置,验证钩码和滑块所组成的系统从由静止释放到通过光电门这一过程机械能守恒.实验开始时,气轨已经调成水平状态.

(1)已知遮光条的宽度为d,实验时将滑块从图示位置由静止释放,由数字计时器读出遮光条通过光电门的时间为t,则滑块经过光电门时的速度为______.

(2)在本次实验中还需要测量的物理量有(文字说明并用相应的字母表示):钩码的质量m、______和______.

(3)本实验通过比较______和______(用测量的物理量符号表示)在实验误差允许的范围内是否相等,从而验证系统的机械能是否守恒.

阅读理解

When I lived in Spain, some Spanish friends of mine decided to visit England by car. Before they left, they asked me for advice about how to find accommodation (住所). I suggested that they should stay at “bed and breakfast” houses, because this kind of accommodation gives a foreign visitor a good chance to speak English with the family. My friends listened to my advice, but they came back with some funny stories.

“We didn’t stay at bed and breakfast houses,” they said, “because we found that most families were away on holiday.”

I thought this was strange. Finally I understood what had happened. My friends spoke little English, and they thought “VACANCIES” meant “holidays”, because the Spanish word for “holidays” is “vacaciones”. So they did not go to house where the sign outside said ‘VACANCLES’, which in English means there are free rooms. Then my friends went to house where the sign said ‘NO VACANCLES’, because they thought this meant the people who owned the house were not away on holiday. But they found that these houses were all full. As a result, they stayed at hotels!

We laughed about this and about mistakes my friends made in reading other signs. In Spanish, the word “DIVERSION” means fun. In English, it means that workmen are repairing the road, and that you must take a different road. When my friends saw the word “DIVERSION” on a road sign, they thought they were going to have fun. Instead, the road ended in a large hold.

English people have problems too when they learn foreign languages. Once in Paris. when someone offered me some more coffee, I said ‘Thank you’ in French. I meant that I would like some more, However , to my surprise the coffee pot was taken away! Later I found out that ‘Thank you’ in French means ‘No, thank you.’

1. My Spanish friends wanted advice about ______.

A. learning English                     B. finding places to stay in England

C. driving their car on English roads        D. going to England by car

2. I suggested that they stay at bed and breakfast houses because ______.

A. they would be able to practise their English

B. it would be much cheaper than staying in hotels

C. it would be convenient for them to have dinner

D. there would be no problem about finding accommodation there

3. “NO VACANCIES” in English means ______.

A. no free rooms        B. free rooms      C. not away on holiday    D. holidays

4. If you see a road sign that says ‘Diversion’, you will ______.

A. fall into a hole

B. have a lot of fun and enjoy yourself

C. find that the road is blocked by crowds of people

D. have to take a different road

5. When someone offered me more coffee and I said “Thank you” in French, I ______.

A didn’t really want any more coffee      B. wanted them to take the coffee pot away

C. really wanted some more coffee        D. wanted to express my politeness