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一、选择题:(每小题5分,共30分)1.一个人想用长为l的竿子打在岩石上的办法把竿子折断,为此,他用手拿住竿子的一端,让竿子绕该端作无位移转动,此人希望当竿子打在岩石的瞬时,手受到的冲击力最小,问竿子离手多远的地方打在岩石上最好?(不计竿子重力)(A)l.(B)l/2.(C)2l/3.(D)l/3.()2.图(1)是半径为R的匀质细圆环,悬挂在O 相似文献
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值得重视的定性,半定量物理实验 总被引:2,自引:0,他引:2
本文明确提出了一类新的实验一定性、半定量的物理实验,论述了这类实验在培养学生创新能力方面的作用和意义,最后介绍了国外及作者在这方面的实践情况。 相似文献
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第九届非物理类专业大学生物理竞赛试题及解答(1992)试题一、选择题(每小题3分,共30分)1.一个人想用长为l的竿子打在岩石上的办法把竿子折断,为此,他用手拿住竿子的一端,让竿子绕该端作无位移转动,此人希望当竿子打在岩石的瞬时,手受到的冲击力最小,... 相似文献
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Investigation the positive moments on the M-T curve of YBCO films measured by using zero-field cooling 下载免费PDF全文
The superconducting transition of a YBCO film was measured by a MPMS-5 superconducting quantum interference device magnetometer, using a zero-field cooling process. The experimental results have shown that there are positive magnetic moment and positive peak on the M-T curve. We have proven that these anomalous behaviours are due to measurement error, but not phase transition. We have proposed a simple formula to explain and to calculate quantitatively these anomalous behaviours. It was found that, provided dH>0.59Hp (dH is the inhomogeneous field of the remnant field, Hp is the fully penetrated field of the measured sample), the experimental results will be positive, not negative. If dH≥2Hp, the experimental results will be symmetrical to their real negative values. From the M-T curve, which has positive moment and positive peak below Tc (superconducting transition temperature), we found a new possible method to obtain Hp of the measured sample. 相似文献
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让NdFeB小磁体在铝管中下落,通过改变铝管及NdFeB小磁体的尺寸,测量出NdFeB小磁体的下落时间.通过数据分析,得出了一些有用的结论,可供制作此类仪器者参考. 相似文献
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