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毽子为何总是底盘着地

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石头 发表于 2011-11-3 11:11:58 | 显示全部楼层 |阅读模式
本帖最后由 石头 于 2011-11-3 11:12 编辑

       从物理的角度说,毽子属固体。虽然羽毛部分比较容易因受力而发生形变,但在可以接受的范围内的受力之后,羽毛仍会由于弹性回到初始的形状。所以在空中运动时,毽子可以被看做一个硬的固体,就是说形状受空气影响所发生的形变可以忽略不计。铜钱的密度是远大于羽毛的,所以单独的铜钱下坠的速度会比单独的羽毛的大。当二者接在一起的时候,铜钱会对羽毛有一个向下的力,而羽毛则对铜钱会有一个向上的力。
        由于严格说来毽子属不规则物体,在空气阻力的作用下,相互的推力极难保持稳定,这种推力就有向牵引力发展的趋势。由此,这样一个硬固体,在受到重力和空气阻力的作用下,在物体内重心所在位置必定要向更接近重力的方向偏转。当密度大的铜钱的重心在下,密度小的羽毛的重心在上,并且后者重心至前者重心的连线指向重力方向时,铜钱对羽毛的牵引力无法再因偏转而增大。此时毽子的整个重心正好在铜钱重心与羽毛重心的连线上,而且更接近密度大的重心一端,毽子保持稳定,不再偏转。直到最后铜钱一端与地面发生碰撞……

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新辉 发表于 2011-11-3 19:19:24 | 显示全部楼层
石头好利害,这么专业的难题还回答得这么详细。
期待下次从化学的角度谈一下。
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敲牧依依 发表于 2012-2-10 20:55:16 | 显示全部楼层
不错的~~! 感谢您提供












胶原蛋白粉 http://www.b008.com
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迪巴殿 发表于 2012-4-27 20:55:55 | 显示全部楼层
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shenmina 发表于 2012-5-20 20:42:42 | 显示全部楼层
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rgzaz 发表于 2012-8-14 21:11:44 | 显示全部楼层
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angelabr 发表于 2012-9-22 14:24:41 | 显示全部楼层
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迟心标 发表于 2012-9-29 16:15:38 | 显示全部楼层
这个贴不错!











华山仙门
天地霸气诀
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ylyizjek 发表于 2012-10-28 05:25:42 | 显示全部楼层
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shfafsdk 发表于 2012-11-11 02:00:52 | 显示全部楼层

National drought farmland exceeds 100 million mus

The State Flood Control and Drought Relief Headquarters Office statistics,abercrombie, as of May 29th, countrywide farmland drought area of 104400000 mu.The middle reaches area of Yangtze River in Hubei, Hunan, Jiangxi, Anhui, Jiangsu 5 provinces drought is severe.
Hubei, Hunan, Jiangxi, Anhui, Jiangsu 5 provinces farmland drought area is 45350000 mus, occupy countrywide drought area 43.4%.The 5 has 3290000 people,http://www.franklinsmarshallnboutiquefr.com, 950000 head of livestock drinking water difficulties because of drought, respectively,The owner, county call you to delete posts
. this year 44 years old, had been engaged in enterprise management work.In May 16th, she was the for Thais party push to the front, and in the July 3rd parliamentary elections defeating Abhisit, house a total of 500 seats, as the Thai Party won 265 seats, Democrats won only 159 seats., accounting for 50.
6% of the country and 24%.The bumper harvest of summer grain crops drought had little influence on early rice rice, part by the threat of water shortage state flood prevention and Drought Resistance Headquarters Office statistics, as of May 29th, countrywide farmland drought area of 104400000 mu.
The middle reaches area of Yangtze River in Hubei, Hunan, Jiangxi, Anhui, Jiangsu 5 provinces drought is severe.National Air relevant responsible person said, the middle reaches area of Yangtze River in 1978, 1981, 1986,mercurial vapor pas cher, 1994, 2000 had more serious spring drought, but this year drought of high intensity,mercurial vapor, long duration, range is wide, influence degree etc.
.Since May 20th,jordan pas cher,Carrefour was exposed boxed fresh withdraw goods date being
. this year 44 years old, had been engaged in enterprise management work.In May 16th, she was the for Thais party push to the front, and in the July 3rd parliamentary elections defeating Abhisit, house a total of 500 seats, as the Thai Party won 265 seats, Democrats won only 159 seats., the drought in downstream in the Yangtse River a significant rainfall process.National Defense Office Deputy Director Zhang Xu said,air jordan, the rainfall to alleviate the current South drought favorable, part of soil moisture was significantly improved, for transplanting, soil moisture replant effect is obvious.
But because the rainfall duration is not long, not the overall rainfall runoff, did not form an effective, to improve the water level of rivers, lake reservoir is not the role of increased.Zhang Xu said, the middle lower reaches of the Yangtze River in the peak of water, agricultural water pressure is very great.
At the same time, because of the early water consumption is larger, drinking water problems become more prominent, drought situation is still severe.According to introduction, the drought affected Hubei, Jiangxi, the middle reaches area of Yangtze River is not the main wheat producing areas, the drought had little influence on the bumper harvest of summer grain crops.
But affected by drought, part of rice due to water cannot timely planting, planting also because has no water growth affected,www.burberrysoldes-boutique.com; rice seedling raising and transplanting is also affected by the threat of water shortage.
Less rainfall,Jiangsu Changzhou development zone net exposure to spend 920000 money to pay.
. this year 44 years old, had been engaged in enterprise management work.In May 16th, she was the for Thais party push to the front, and in the July 3rd parliamentary elections defeating Abhisit, house a total of 500 seats, as the Thai Party won 265 seats, Democrats won only 159 seats., insufficient main reason is heavy drought in "land of plenty" is facing such a severe drought? National Defense Office official said, in part because of severe lack of precipitation.According to the analysis, this year the middle reaches area of Yangtze River precipitation and compared to six years less, for the years 1951 since the same period,www.abercrombieeandfitchffrance.com.
Enter after May, although precipitation a slight increase in the previous period, but Hubei, Hunan,franklin marshall, Jiangxi, Anhui, Jiangsu provinces precipitation and history compared to the same period two to four is relatively small.
On the other hand,air jordan, is because the river water shortage, water is serious on the low side.The precipitation slants apparently little effect, lower reaches of the Yangtze River main river accumulated water quantity is less a year earlier to 70%.
National air data shows, May 29th 8, Poyang Lake Xingzi water level 10.79 meters, 4,mercurial pas cher.64 meters lower than the same period; the Dongting Lake station of Chenglingji water level 23.71 meters, 2.82 meters lower than the same period,air jordan pas cher.
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pijft 发表于 2013-2-14 13:57:16 | 显示全部楼层
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磊晨峰 发表于 2013-3-5 06:15:42 | 显示全部楼层
有意义,有收获,谢谢提供












唐寅在异界
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eitheodg 发表于 2013-3-8 23:45:03 | 显示全部楼层

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August 12, 2010 15:30, furnace serious burst Yang Village Industrial Park of Zibo District of Zichuan City, Shandong Sidanke Ceramics Co., Ltd gas station and gas occurrence.After the incident, the public security, safety supervision have been rushed to the scene.According to the understanding, the time of the incident, explosion, collapse of gas producer, at present, Zichuan power supply department staff is repair line.The cause of the accident is under investigation.
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