题目

 (1)用自由落体法验证机械能守恒定律，下面哪些测量工具是必需的？___________ (A) 天平     (B) 弹簧秤    (C) 刻度尺    (D) 秒表 (2) 如图是实验中得到的一条纸带。已知打点计时器所用电源的频率为50Hz， 当地的重力加速度 g＝9.80 m／s2，测得所用重物的质量为1.00kg，纸带上第0、1两点间距离接近2mm，A、B、C、D是连续打出的四个点，它们到O点的距离如图所示，则由图中数据可知，重物由O点运动到C点，重力势能的减少量等于________J，动能的增加量 Where do you think people will live in the future? Can you imagine people work and live in the sea? But how will people go to work then? By submarine (潜水艇)!Some scientists believe that some day submarines will be as many as today’s car. A famous French driver says, “One day, man will work on the ocean floor as they do on the street!”If people want to live in the sea, they have to solve a lot of problems first. Some of these problems, similar to those of living on the moon, are that there isn’t enough oxygen and people may be in weightless（失重的） conditions. Many questions are hard to answer. For example, what will happen to our bodies if we live in the sea for a very long time? Scientists are looking for answers.Maybe in 50 years man will be able to live in the sea, away from the crowded and noisy cities on land. Man will find it fun and interesting to live in the sea. And life in the sea is more comfortable. Don't you think so?1.Maybe people in the future will_________ to work on the ocean floor.A. drive a car B. take a bus C. take a submarine D. swim2.What do people have to do first before living in the sea?A. People have to build houses first.B. People have to learn to swim first.C. People have to learn to drive the submarine first.D. People have to solve some problems first.3.What problem will people have if they live in the sea?A. They will have difficulty in breathing. B. They will become quite short.C. They will feel cold. D. They will feel tired.4.The writer thinks living in the sea is _______ than living on land.A. more comfortable B. less comfortable C. easier D. more crowded5.Which of the following is NOT true according to the passage?A. There are also some problems for people to solve if they want to live in the sea.B. The sea is noisy and crowed for man to live in.C. Some of the problems are very hard to solve.D. Some scientists believe submarines will be popular in the future.