1stsightlove
幼苗
共回答了12个问题采纳率:91.7% 举报
同时浸没在水中时:
F甲=G甲-p水G甲/p甲=G甲(p甲-p水)/p甲
F乙=G乙-p水G乙/p乙=G乙(p乙-p水)/p乙
F甲=F乙
G甲(p甲-p水)/p甲 = G乙(p乙-p水)/p乙 .(1)
同时浸没在酒精中时:
F'甲=G甲-p酒精G甲/p甲=G甲(p甲-p酒精)/p甲
F'乙=G乙-p酒精G乙/p乙=G乙(p乙-p酒精)/p乙
F'甲>F’乙
G甲(p甲-p酒精)/p甲 > G乙(p乙-p酒精)/p乙 .(2)
(2)÷(1):
(p甲-p酒精)/(p甲-p水)>(p乙-p酒精)/(p乙-p水)
(p甲-p酒精)(p乙-p水) > (p甲-p水)(p乙-p酒精)
p甲p乙-p水p甲-p酒精p乙+p水p酒精 >p甲p乙-p酒精p甲-p水p乙+p水p酒精
-p水p甲-p酒精p乙 > -p酒精p甲-p水p乙
p水p乙-p酒精p乙 > p水p甲-p酒精p甲
(p水-p酒精)p乙 > (p水-p酒精)p甲
p乙>p甲
由(1)得:
G甲(p甲-p水)/p甲 = G乙(p乙-p水)/p乙
G甲/G乙 = [(p乙-p水)p甲] / [(p甲-p水)p乙] = (1-p水/p乙) / (1-p水/p甲)
(G甲-G乙)/G乙 = (1-p水/p乙-1+p水/p甲) / (1-p水/p甲)
= (p水/p甲-p水/p乙)/(1-p水/p甲)
= p水(p乙-p甲)/[p乙(p甲-p水)]
p乙-p甲>0,p甲-p水>0
∴(G甲-G乙)/G乙>0,G甲>G乙
∴B正确
1年前
10