问题 实验题

小明在探究了“杠杆平衡条件”后,认为:杠杆的平衡条件是,动力乘以支点到动力作用点的距离等于阻力乘以支点到阻力作用点的距离。请利用图中的实验器材证明小明的观点是错误的。写出简要的实验步骤及实验现象。

答案

用弹簧测力计斜向上拉杠杆,使杠杆在水平位置平衡,此时动力乘以支点到动力作用点的距离不等于阻力乘以支点到阻力作用点的距离。所以小明的观点是错误的。

阅读理解

There are about 80,000,000 mines*  under the ground in more . than 60 countries. It is difficult and dangerous to clear these rnines, About 50  people including many children were’ killed ‘or htirt each iay.  In 2003,  APOPO,  a Dutch research com pan y that uains the an imals, came up with the-idea of s\ng rats to search for the mines.

The animal trainers ‘found that a kind of rats from Africa were clever and had.a sharp*  sense of smell.  The rats were about 75 cm long and.weighed about l.35 kg, light enough to run across a minefield without setting off the mines.

In January 2004, the APOPO started this project. First, the trainers let the 4-week-old baby rats get familiar with humans. A few weeks later, the rats were no Ionger afraid of people and ‘the things around them. Then they were trained to connect a click* sound with food. After the rats had leamed that, the trainers then taught them to tell the difference between the smell of mines and other smells. When the rats could do it, the click was sounded and they were given a bit of banana.  The method was called clicker training. “The training isn’t easy, said trainer Abdullah Mchomvu.  “You have to be patient. Sometimes I get angry, but then again, I tell myself these are animals.”

After nine months’training, the rats were taken to a minefield. They’ran across the minefield, stopped, sat and scratched the ground to tell the deminers*  that they smelt out’a mine.  Then the mine was cleared. It had  taken two ‘deminers  a day to clear a 200㎡ . minefield, but with the help of two rats ‘they could finish it in two hours.

The rats and the deminers saved thousands of lives, “The rats did this job much better than we expected. So far they have helped to make almost 2,000,000㎡ of land safe. They are heroes,” said Bart Weeqens, the head of the APOPO.

小题1: The APOPO trained the rats to search for     .

A.children

B.animals

C.mines

D.bananas小题2: While training the rats, the trainers have to be

A.patient

B.clever

C.brave

D.serious小题3: How long did the training last?

A.Two hours.

B.One day.

C.Four weeks.

D.Nine months.小题4:Which of the following is NOT TRUE according to the passage?

A.Each day about 200 people were killed or hurt by mines,

B.The APOPO started to train the rats in January 2004.

C.The trainers gave the rats food after they smelt out a mine.

D.The rats and the deminers saved thousands of lives.

问答题 简答题