题目

“舂米对”是一种简单机械，其示意图如图所示。使用这个装置时，人在A端用力竖直把它踩下后立即松脚，B端石块就会立即下落，打在石臼内的谷物上，从而把谷物打碎．你认为它属于（填“费力”还是“省力”）杠杆，舂米的过程中装置从水平转过角度小于70°，则此过程中脚所施加的力如何变化。 答案：【1】费力【2】逐渐变小Because plants cannot move or talk, most people believe that they have no feelings and that they cannot receive signals from outside. However, this may not be completely true.People who studied plants have found out that plants carry a small electrical charge (电荷). It is possible to measure this charge with a small piece of equipment called “galvanometer”. The galvanometer is placed on a leaf off the plant, and it records any changes in the electrical field of the leaf. Humans have a similar field which can change when we are shocked or frightened.A man called Backster used a galvanometer for his studies of plants and was very surprised at his results. He found that if he had two or more plants in a room and he began to destroy one of them － perhaps by pulling off its leaves or by pulling it out of its pot － then the galvanometer on the leaves of the other plants showed a change in the electrical field. It seemed as if the plants were signalling a feeling of shock. This happened not only when Backster started to destroy plants, but also when he destroyed other living things such as insects (昆虫).Backster said that the plants also knew if someone had destroyed a living thing some distance away, because they signalled when a man who had just cut down a tree entered the room.Another scientist, named Sauvin, achieved similar results to Backster’s. He kept galvanometers fixed to his plants all the time and checked regularly to see what the plants were doing. If he was out of the office, he telephoned to find out about the signals the plants were sending. In this way, he found that the plants were sending out signals at the exact times when he felt strong pleasure or pain. In fact, Sauvin could cause a change in the electrical field of his plants over a distance of a few miles simply by thinking about them.【小题1】Backster was surprised at the results of his studies because _____.A．he destroyed an insectB．he destroyed a plant by pulling off its leavesC．he found that plants could express feelings of shockD．he found that plants could move and speak after all【小题2】The plants sent out signals _____.A．only when Backster Started to destroy plantsB．when Backster destroyed plants or other living thingsC．only when he destroyed things such as insectsD．only when Backster placed the galvanometer on the leaves of the plants【小题3】The scientist called Sauvin _____.A．did not agree with Backster’s ideasB．did not get the same sort of results as Backster didC．got different results from Backster’sD．found out some of the same things that Backster did【小题4】Which of the following is true according to the passage?A．The electrical charge plants carry may shock or frighten us.B．A tree will signal when it has been cut down.C．Sauvin could make his plants send out signals some distance away.D．Plants have feelings because they can receive signals without moving.