题干

五一假期,小华同学的全家去旅游,在高速路上看到如图所示标志牌,小华发现小轿车、大型客车、载货汽车最高行驶速度不同.爱思考的小华想:为什么要对机动车的最高行驶速度进行限制?为什么在同样的道路上,对不同车型设定不一样的最高行驶速度?请你从“能量”角度,用相关知识解释此现象.

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解:机动车质量一定,速度越快,动能越大,刹车时制动距离越大,容易出现交通事故,所以要限速行驶;

在相同的道路上,不同车型的机动车质量不同,速度相同时,质量大的动能大,制动距离大,质量小的动能小,制动距离小,当制动距离相同时,不同车型限速就不同.

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    In 1863, the great novelist Jules Verne wrote a novel called Paris in the Twentieth Century. In the book he used the full power of his great ability to forecast the coming century. Unfortunately, the manuscript (手稿) was lost until his great-grandson happened to discover it lying in a safe where it had been carefully locked away for almost 130 years. Realizing what a treasure he had found, he arranged to have it published in 1994, and it became a bestseller at once.

    Back in 1863, kings still ruled the ancient world in Europe, with so many poor people working in the fields. And steam power was just beginning to change the world. But Verne predicted that Paris in 1960 would have glass skyscrapers, air conditioning, TV, high-speed trains, gas-powered vehicles, and even something similar to the Internet. Verne described life in modem Paris almost without any mistakes.

    Just two years later Verne made another amazing prediction. He wrote From the Earth to the Moon, in which he predicted the details of the task that sent several astronauts to the moon 100 years later in 1969. He correctly predicted the size of the space capsule, the number of astronauts who would carry out the task, the weightlessness that the astronauts would experience, and the final landing in the ocean.

    How was Jules Verne able to predict 100 years into the future successfully? Although he was not a scientist himself, Verne often turned to scientists, asking them questions about their opinions of the future. He collected a vast amount of information about the great scientific discoveries of his time. Verne realized that science would make it possible for many amazing things to appear in the future. The secret of his successful prediction was his belief in the power of science to change society.