(1)从图甲得:GA+GB= F拉1+ F浮,从图乙得:GA+GB=F拉2,从图丙得:2F1= F拉1+ GC, ∴2F1=GA+GB+ GC- F浮,从图丙得:2F2= F拉2+ GC, ∴2F2 =GA+GB+GC, , 8F浮 =5(GA+GB+GC) ①,物体A和浮筒浸没在水中时η1= 80%, , F浮=GA+GB- 4GC ②, ①、②两式联立解得: 3(GA +GB) =37GC, GA+ GB=GC =×0.6 N =7.4 N, GB=GC=×0.6 N =0.8 N, GA=7.4 N -0.8 N =6.6 N, 物体A和浮筒出水后, ; (2)F浮= GA +GB- 4GC = 6. 6 N +0. 8 N - 4×0. 6 N =5 N, F浮A= F浮- F浮B = F浮-5GB =5 N- 5 ×0. 8 N=l N, , ρA=×1×103 kg/m3 =6.6 ×103 kg/m3 。 |