如图所示为某实验装置示意图,A,B、O在同一竖直线上,一根轻质弹性绳一端固定在天花板上A点,另一端绕过B处的定滑轮后系在一个质量为m = 0.8 kg的小物体上,小物体置于地面上O处时,弹性绳中弹力为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmfrac%3E%3Cmn%3E1%3C%2Fmn%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmfrac%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
mg,将小物体向右推到O
1点,OO
1距离为x
1 = 0.3 m,小物体由静止释放,并水平向左滑行,当小物体经过O点时与弹性绳脱离,之后恰能运动至M处,OM距离为s = 0.075 m,已知弹性绳原长等于AB距离,且始终不超过弹性限度,弹性势能为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3EE%3C%2Fmi%3E%3Cmtext%3Ep%3C%2Fmtext%3E%3C%2Fmsub%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmfrac%3E%3Cmn%3E1%3C%2Fmn%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmfrac%3E%3Cmi%3Ek%3C%2Fmi%3E%3Cmsup%3E%3Cmrow%3E%3Cmo+stretchy%3D%22false%22%3E%28%3C%2Fmo%3E%3Cmtext%3E%CE%94%3C%2Fmtext%3E%3Cmi%3El%3C%2Fmi%3E%3Cmo+stretchy%3D%22false%22%3E%29%3C%2Fmo%3E%3C%2Fmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,∆l为形变量大小,小物体与地面的动摩擦因数为μ = 0.5,g = 10m/s
2。求: