两个金属圆柱体竖立在水平桌面上，它们的底面积之比是8：9，密度之比是9：8，桌面受到的压强之比是3：2，那么这两个金属圆柱体的高度之比是______．
圆柱体对水平桌面的压强为：
P=
=F S
=G S
=mg S
=ρVg S
=ρgh，ρShg S
因ρ1：ρ2=9：8，P1：P2=3：2，
所以根据h=
可得：p ρg
=h1 h2
=P1 ρ1g P2 ρ2g
×P1 P2
=ρ2 ρ1
×3 2
=8 9
．4 3
故答案为：4：3．
完形填空。 | ||||
| Last Sunday I took my son to the zoo 1 the morning. I wanted my son 2 more about animals. We 3 the No. 8 bus to the zoo. First we went to see the fishes and the birds. My son was very 4 . And he asked me a lot of questions. "Don't always ask 5 . Please use your head." I told the boy. After we left the birds, my son 6 me that he wanted to have a rest. I looked 7 and found a long chair under a tree. When we came to the chair, I saw a card 8 it. It said, "Don't take the seat. The paint is wet." We had to see some monkeys, foxes, elephants. Then we saw some tigers and leopards. "Dad," my son said to me, " 9 I tell you a secret?" "Of course. What is it?" "I know where the spots of the leopards come from," said my son. "They come from the 10 ." "Why?" "Please look at the paint of the cage. It is wet now." | ||||
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