作者monmath (烽火狼烟血樱飘杀)
看板Physics
标题Re: [题目] 白努力定律的题目2
时间Mon Jun 18 18:19:30 2007
※ 引述《topractise (连月亮都帮我!)》之铭言：
: Water pressurized to (3.5 x 10^5) Pa is flowing at 5.0m/s in a horizontal pipe
: which contracts to 1/3 its former area. What are the pressure and velocity of
: the water after the contraction ?
: (A) 2.5 x 10^5 Pa , 15m/s
: (B) 3.0 x 10^5 Pa , 10m/s
: (C) 3.0 x 10^5 Pa , 15m/s
: (D) 4.5 x 10^5 Pa , 1.5m/s
: (E) 5.5 x 10^5 Pa , 1.5m/s
: 请问是A还是C呀...要怎麽算勒
体积不可压缩：A1*v1=A2*v2
=>A*5=(1/3)A*v2
=> v2=15
Bernoullie(也许拼错XD) equation:
P1+(1/2)*d*v1^2=P2+(1/2)*d*v2^2
3.5*10^5+0.5*1000(SI unit)*5^2=P2+(1/2)*1000*15^2
P2=2.5*10^5
so...(A)
算散射算到很烦...= =
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1F：推 topractise:SO GA!刚温~ 06/18 19:11
2F：推 equation02: test 12/14 17:20