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This month' s income tax deadline might inspire fantasies of fleeing Earth. But the laws of physics, like the laws of the IRS, are irrevocable. Before you can set up a tax shelter on Mars, there's that little matter of achieving escape velocity. Getting off our planet requires a textbook speed of 6.96 miles per second. That number applies only if you want to wrench free from Earth's gravity in a one-shot effort, however. If you can wait, a slow, steady thrust can also do the job. Think of Earth as lying at the bottom of a pit. If you drop a rock into the pit, it will have a certain velocity when it hits bottom. One way to get out of the hole is to jump upward at the exact same speed-the escape velocity. Another way out is to climb gradually up the wall of the pit. So long as you generate enough force to keep working your way up the wall, you' II still get out. Heading upward at even one mile per hour, a rocket could work its way out of Earth' s gravitational field travel clear across the universe if its engine fired for a long enough time. 相似文献
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王立娥 《教学月刊(中学下旬版)》2003,(9):27-28
新课程强调体验性学习,要求学生在学习活动中,不仅要用大脑去思考,而且还要用眼睛去观察,用耳朵去聆听,用嘴巴去交流,用双手去操作,也即用自己的身体去感受,用自己的心灵去感悟. 相似文献
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运用统计分析方法分析了5907名大学生的大学英语四级考试听力和阅读成绩,结果显示：阅读成绩、听力成绩和总成绩均呈高度相关,考生的阅读成绩高于听力成绩,听力得分率远低于总成绩得分率。根据分析结果,以图式理论为基础,提出了听读结合的教学模式,使视觉记忆和听觉记忆同时储存在大脑中,帮助学生解决听力困难,提高英语听力理解能力。 相似文献
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新课程强调体验性学习,要求学生在学习活动中,不仅要用大脑去思考,而且还要用眼睛去观察,用耳朵去聆听,用嘴巴去交流,用双手去操作,也即用自己的身体去感受,用自己的心灵去感悟。在教学活动中,笔者曾尝试把生活内容渗透到政治课教学的全过程,使导入、授课、结课始终与生活相连,取得了一定效果。一、利用时代热点,导入新课新的《初中思想政治课程标准》要求,思想政治课要紧密结合时事内容进行教学。思想政治学科是与时代形势紧密结合在一起的学科,用时政热点激发学生学习的兴趣,激活学生思维的兴奋点,就会收到事半功倍之效。如我们一直坚持用… 相似文献
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