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8讲：摩擦Lecture 8: Friction |
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| 课程网址: | http://videolectures.net/mit801f99_lewin_lec08/ |
| 主讲教师: | Walter H. G. Lewin |
| 开课单位: | 麻省理工学院 |
| 开课时间: | 2008-10-10 |
| 课程语种: | 英语 |
| 中文简介: |  |
| 课程简介: | **1. Normal and Frictional Forces:** Starting with a block at rest on a horizontal surface, Professor Lewin describes the normal force, the maximum frictional force that must be overcome to budge the block, and the coefficient of static friction. Once the block is budged and begins to slide, you encounter a smaller coefficient of kinetic friction. **2. Measurements of the Coefficient of Static Friction:** Consider a block at rest on an inclined plane, and increase the tilt until the block just starts to slide. By measuring this tilt angle you can calculate the coefficient of static friction. The friction coefficient only depends on the materials in contact; it is independent of the mass of a sliding object and independent of its surface area (this is rather non-intuitive). **3. Another Way to Measure Friction:** The system consists of a block on an inclined plane. The block is counterbalanced by a second mass connected to the block with a massless string and a near massless, frictionless, pulley. The direction of the frictional force depends on whether the block on the incline wants to move uphill or downhill or stay at rest. By increasing the second mass until the block on the incline budges uphill, you can measure the coefficient of static friction. **4. Ways to Reduce Friction - Fleas are Good for Something!** Scenarios for reducing friction are presented including hydroplanes and air tracks. Even a flea can move a very heavy book if the friction is near zero (as demonstrated). |
| 关 键 词: | 摩擦力; 静摩擦系数的测量; 测量摩擦 |
| 课程来源: | 视频讲座网 |
| 最后编审: | 2020-06-01：吴雨秋(课程编辑志愿者) |
| 阅读次数: | 48 |