如图所示,小明同学在公园荡秋千,已知小明质量为M,秋千的两根绳长均为L,某次荡秋千时绳子与竖直方向最大夹角为37°,当小明荡到秋千支架的正下方时速度为v
1。回到学校,小明把一个质量为m金属小球用细绳悬挂,成为一个摆,摆长为l,最大偏角也为37°,当小球运动到最低点时速度大小为v
2。不计绳的质量和所有阻力,已知sin37°=0.6,cos37°=0.8。当运动到最低点时,下列说法正确的是( )
![](http://tikupic.21cnjy.com/2023/06/21/27/8a/278ad8a9e6b0fd18023f5ddc15bb5b7f.png)
![](http://tikupic.21cnjy.com/2023/06/21/f6/44/f644af2b04678edcada717c27bbc5a74.png)
- A、小明的速度大小v1等于
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsqrt%3E%3Cmrow%3E%3Cmfrac%3E%3Cmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E5%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3Cmi%3Eg%3C%2Fmi%3E%3Cmi%3EL%3C%2Fmi%3E%3C%2Fmrow%3E%3C%2Fmsqrt%3E%3C%2Fmath%3E)
- B、小球的速度大小v2为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsqrt%3E%3Cmfrac%3E%3Cmn%3E4%3C%2Fmn%3E%3Cmn%3E5%3C%2Fmn%3E%3C%2Fmfrac%3E%3Cmi%3Eg%3C%2Fmi%3E%3Cmi%3EL%3C%2Fmi%3E%3C%2Fmsqrt%3E%3C%2Fmath%3E)
- C、秋千对小明的作用力大小为
![](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%3E7%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E5%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3Cmi%3EM%3C%2Fmi%3E%3Cmi%3Eg%3C%2Fmi%3E%3Cmi%3EL%3C%2Fmi%3E%3C%2Fmath%3E)
- D、若绳长变为2l,小球的向心加速度仍为
![](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%3E2%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E5%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3Cmi%3Eg%3C%2Fmi%3E%3C%2Fmath%3E)