如图是上肢力量健身器示意图,杠杆AB可绕O点在竖直平面内转动,
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EA%3C%2Fmi%3E%3Cmi%3EB%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E3%3C%2Fmn%3E%3Cmi%3EB%3C%2Fmi%3E%3Cmi%3EO%3C%2Fmi%3E%3C%2Fmath%3E)
, 配重的重力为120牛,重力为500牛的健身者通过细绳在B点施加竖直向下的拉力为F
1时,杠杆在水平位置平衡,配重对地面的压力为85牛,在B点施加竖直向下的拉力为F
2时,杠杆仍在水平位置平衡,配重对地面的压力为60牛。已知
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmrow%3E%3Cmi%3EF%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsub%3E%3Cmn%3E%EF%BC%9A%3C%2Fmn%3E%3Cmsub%3E%3Cmrow%3E%3Cmi%3EF%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsub%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E2%3C%2Fmn%3E%3Cmn%3E%EF%BC%9A%3C%2Fmn%3E%3Cmn%3E3%3C%2Fmn%3E%3C%2Fmath%3E)
, 杠杆AB和细绳的质量及所有摩擦均忽略不计,下列说法正确的是( )
![](http://tikupic.21cnjy.com/2022/08/02/06/9e/069ee94908afa902d7bce6f8819b4ec9_183x157.png)
- A、配重对地面的压力为50牛时,健身者在B点施加竖直向下的拉力为160牛
- B、配重对地面的压力为90牛时,健身者在B点施加竖直向下的拉力为120牛
- C、健身者在B点施加400牛竖直向下的拉力时,配重对地面的压力为35牛
- D、配重刚好被匀速拉起时,健身者在B点施加竖直向下的拉力为540牛