大学物理 ›› 2020, Vol. 39 ›› Issue (01): 14-17.doi: 10.16854 / j.cnki.1000-0712.190014

• 教学讨论 • 上一篇    下一篇

对一道典型力学问题的思考

王晓颖,王明利,侯岩雪   

  1. 燕山大学理学院,河北秦皇岛 066004
  • 收稿日期:2019-01-11 修回日期:2019-04-10 出版日期:2020-01-20 发布日期:2020-03-01
  • 通讯作者: 侯岩雪,E-mail:houyanxue@ ysu.edu.cn
  • 作者简介:王晓颖(1979—),男,河北唐山人,燕山大学理学院大学物理系副教授,博士,主要从事大学物理教学和非晶合金结构与性能的分子动力学模拟研究工作.
  • 基金资助:
    燕山大学在线课程教改项目(2018XJJG70)资助

Thinking about a typical mechanical problem

WANG Xiao-ying,WANG Ming-li,HOU Yan-xue   

  1. School of science,Yanshan University,Qinhuangdao,Hebei 066004,China 
  • Received:2019-01-11 Revised:2019-04-10 Online:2020-01-20 Published:2020-03-01

摘要: 分析了用悬线将一重球悬挂于天花板下,然后拉重球下方的另一悬线,此后两根悬线谁先断裂这一典型力学问题.结果表明,当拉动悬线的速度v 小于某一临界速度Vc 时,球上方悬线先断裂;当v>Vc 时,则情况较为复杂,具体是上方悬线断裂还是下方悬线断裂取决于悬线能承受的极限张力Fm ;当v>>Vc 时,选取具有合适的Fm 值的悬线,可使得球下方的悬线先断裂.

关键词: 断裂, 临界速度, 极限张力

Abstract:

A typical mechanical problem is analyzed in this paper. A heavy ball is hanged below the ceiling by a rope,and another rope is tied at the bottom of the ball. If the end of the rope moves at a certain velocity,which rope will snap first. The results show that when the moving speed v is less than a certain critical speed Vc,the rope above the ball snaps first. Which rope snaps first when the speed exceeding Vc is decided by the maximum tensile force that the rope can sustain. The rope under the ball snaps first when the speed v>>Vc .

Key words: snap, critical velocity, ultimate tension