小明利用一把刻度尺,一条细线,一个厚底薄壁圆柱形的长杯子(杯壁厚度不计) 和一桶水来测一颗小石头的密度。做法是:将装有适量水的长杯子放入桶内的水中,使杯子竖直漂浮在水面上,如图甲所示,用刻度尺测得杯底到桶中水面的高度
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmi%3E%E2%84%8E%3C%2Fmi%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmsub%3E%3C%2Fmath%3E)
为6厘米,杯底到杯内水面高度
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmi%3E%E2%84%8E%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsub%3E%3C%2Fmath%3E)
为4厘米; 然后把小石头没入杯内水中,杯子继续竖直漂浮在水面上,如图乙所示,用刻度尺测得杯底到桶中水面的高度
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmi%3E%E2%84%8E%3C%2Fmi%3E%3Cmn%3E3%3C%2Fmn%3E%3C%2Fmsub%3E%3C%2Fmath%3E)
为9厘米,杯底到杯内水面高度
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmi%3E%E2%84%8E%3C%2Fmi%3E%3Cmn%3E4%3C%2Fmn%3E%3C%2Fmsub%3E%3C%2Fmath%3E)
为5.5厘米,小明还测得杯子底面积S为20厘米
2。已知水的密度是
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmn%3E1.0%3C%2Fmn%3E%3Cmo%3E%C3%97%3C%2Fmo%3E%3Cmn%3E10%3C%2Fmn%3E%3Cmsup%3E%3Cmi%3E%3C%2Fmi%3E%3Cmn%3E3%3C%2Fmn%3E%3C%2Fmsup%3E%3C%2Fmath%3E)
千克/米
3。则这块小石头的密度是
千克/米
3。
![](http://tikupic.21cnjy.com/2025/02/11/32/6c/326c5315022ab68dcc0199b946e273cf.png)