力学第十二章

1、 A.?h 50h h h cm(2)?设.1234.解 答. P ,0P1,P,P A ,P :23AP P gh101P2 P g h12P P gh323 P ghP:A34PA P gh h g h h ) () 2.43atm0134250 .h?解 答求,PP,P以P 以ABAB以,则PAPBPghA2 P ( )g h hB1 P PghAB, .cm m宽 m m,.解 答ObxEz21aF 1 02220FAB.dz1y0z2C DF 20222z405:112 ( )F F 1N2262 , . ,设h 50 BN /m2?解 答:P P gh0B:P P 6.664 (N

2、/m )420B1.03g/cm300m.(2) (1) ,31.解 答P P 0 533.1 (N /m )62 .1g0P gp00 , /m ,y m:P53300P3.1810 pa4 ;若容器以竖直向上的加速度a;( g)若容器以竖直向下的加速度a解 答., .dyS dP P(PdPS PS和 P和 ,mg . yao may f.406:PS (PdPS mgma 0 SdymP(PdP) dyg dya0()dP ga dy ( )PydPg a dyPy(00PP ga y y)()00)()(P P ga y y00 gag 0.P P,a0 P (ga).h y ya.P

3、00 P (ga).a, P0h. b h,a.解 答.b xy建立坐标系o,在柱面上取一窄条,窄条的面积S abd:axdF P g h y dS ()0asinydFdxdF P g ha (abdsin) dF0dFdF P g ha (abdsin) cosyyx0dF P g(haabdsin) siny0F P g(haxabsin) cos d200 (P gh abd1 )sin singa bdsin22000aP g(h)20F P g(haabsin) sin d2y00 (P gh abd0 )cos sin ga bd222010P g(ha)40aa2F F F a

4、b P g(h) P g h (22224xy00407F 则a) (P g h0FyF4tgtg11a (P g h0)x2F . 1m m,0.5mh解 答. xyx yomR,h,P 1.013 N/m520:RF RP g(h (N)F 与x)42x0 xRF P g(h ( )N44y0F F F (N)224xyFyFtgtg 1.01545 11x .O(x,y) xRcos m )yR m ) m, .解 答S O. ,.移xxf x 0.x 0., f :xxx408d x2 0s mdt2x 20mmT 0 m,.解 答 , 向上.oy.P()P0 0P00P P00Pgd

5、p dyP00 dp gPydy0PPP000Pgn y0P0P00ggy Pe m1.1610 ( )4 1P PeP y0000P0P Pe104 y0P Pe0.65510 (N /m )10452布0Pe104 64.7%布P0 , h深Hh.(1) x,(2)hH?解 答 2x:4092(H h)t g:2(H h)x t 2gh 2 h(H h)2g.h :2 (H h) 2 h(H h)(H h)h(H h) ( )0h h22: ( )0h h22H H 4(2h)22hH h 2hH. ,H?解 答:x2 h(H h)0dx 2H 2h h(H h) (H h)h(1)而故1

6、/2dh 2h(Hh)HHhh.22H将h:2HHx 2(H ) H22 A 流 A ,S 和S大h:,用 12S2221P P gh )010S410即S A.1解 答PCh12PSS012E0P0AB,SCS对12.12 P ; P)2002112P 1 P 21)22022 2S S1 1:2 2S 212S1S S又1212S2221 ) (1 gh )0P P 222110S1 A和B S S A2CDS S 求E(液空气AD解 答23 1D PC0A E 023PP2Eh3BD :4111212 (P g h h P ) P 222302120:1C 又D 3SSS SC22DE 因?: E 液空气P P gh023: 2 ( g h h)2321SS2 8 ( ) g h h222323D221C1 () 8( )g h hP P g h h 2202121 P 3 g h h ()021P Ph 3h h)20g21 ,.解 答P10h h h213P0E 02 3 4P 由.1112P P P P 2223222012304:4 4S S S2 23 3S SS234 234 P P P230,hh23412P P gh202P P gh303h 0