试题详情
如图所示,一弹性轻绳
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmo%3E%28%3C%2Fmo%3E%3C%2Fmath%3E)
绳的弹力与其伸长量成正比
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmath%3E)
一端固定在
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EA%3C%2Fmi%3E%3C%2Fmath%3E)
点,弹性绳自然长度等于
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EA%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3EB%3C%2Fmi%3E%3C%2Fmath%3E)
, 跨过由轻杆
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EO%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3EB%3C%2Fmi%3E%3C%2Fmath%3E)
固定的定滑轮连接一个质量为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3Em%3C%2Fmi%3E%3C%2Fmath%3E)
的绝缘带正电、电荷量为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3Eq%3C%2Fmi%3E%3C%2Fmath%3E)
的小球。空间中还存在着水平向右的匀强电场
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmo%3E%28%3C%2Fmo%3E%3C%2Fmath%3E)
图中未画出
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmath%3E)
, 且电场强度
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EE%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmfrac%3E%3Cmrow%3E%3Cmi+mathvariant%3D%22normal%22%3Em%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3Eg%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmi+mathvariant%3D%22normal%22%3Eq%3C%2Fmi%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3C%2Fmath%3E)
。初始时
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EA%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EB%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EC%3C%2Fmi%3E%3C%2Fmath%3E)
在一条竖直线上,小球穿过水平固定的杆从
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EC%3C%2Fmi%3E%3C%2Fmath%3E)
点由静止开始运动,滑到
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EE%3C%2Fmi%3E%3C%2Fmath%3E)
点时速度恰好为零。已知
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EC%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EE%3C%2Fmi%3E%3C%2Fmath%3E)
两点间距离为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EL%3C%2Fmi%3E%3C%2Fmath%3E)
,
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3ED%3C%2Fmi%3E%3C%2Fmath%3E)
为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EC%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3EE%3C%2Fmi%3E%3C%2Fmath%3E)
的中点,小球在
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3EC%3C%2Fmi%3E%3C%2Fmath%3E)
点时弹性绳的拉力为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmfrac%3E%3Cmrow%3E%3Cmn%3E3%3C%2Fmn%3E%3Cmi+mathvariant%3D%22normal%22%3Em%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3Eg%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3C%2Fmath%3E)
, 小球与杆之间的动摩擦因数为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmn%3E0.5%3C%2Fmn%3E%3C%2Fmath%3E)
, 弹性绳始终处在弹性限度内。下列说法正确的是
( )
![](http://tikupic.21cnjy.com/2024/03/22/fc/87/fc87d60c0c7fab04f99643dd5e936f99.png)
知识点
参考答案