Everyobjecthasweight的精选

问题详情：   Everyobjecthasweight.Butthecenterofitsweightisnotalwaysinthemiddleoftheobject.Ifthetopofanobjectisheavierthanitsbottom,itwillfallovereasily.Wesaythatitscenterofgravity（引力）ishigh.Butifthe...