C. sd phan tfi (hay nguydn tfi) ed tron g1 don vi khdilugng khị D sd nguydn tfi cd trong 12 g cacbon 12.
CO HOC CHnt LiAl 5.1 cauC.
5.1. cauC. 4 D^ ^ 4 0 03^ 5.2. m = pV = P ^ T : ^ = 7 , 8 . 1 0 ^ ^ . 3 , 1 4 . ^ ^ = 0,11 kg. 3 2 3 2 m 131 3 3 ’ ’ ’
5.3. p = T7 = ^ T = 10,48.10 kg/m Dd’i chid’u vđ Bdng khdi luang rieng V 0,05^
ciia mgt sd chdt (xem phu luc 2 SGK) thi đ la khdi lugng ridng cua bac (trong SGK la 10,5 g/cm^). 5.4. p = 1 1 ^ = - 5 0 : 9 ^ = 0,39.10^ N/m^ S 3,14.0,02^ 5.5. p = Pa + pgh = 1,01.10^ + 1,0.10^9,8.30 = 3,95.10^ Pạ 5.6. F J = Fl | 2 . = 15 000. - ^ = 225 N. ^ ^ Sl 200 5.7. a) Ta cd : ViSi = V2S2, hay V2 = Vi ^ = = 10 m/s. S2 5
b) Ap dung dito luat Bec-nu-li eho hai vi trf 1 va 2 :
1 2 1 2 Pl + 2"P^i = P2 + -j^^i suy ra : Pl = P2 + -p(v^ - vJ.) = 2.10^+ -.1.10^ (100-25) = 2,375.10^N/m^ c) A = vS = ViSi = 5 m/s.0,001 m = 0,005 m^/s = 0,3 m^/min. 5.8. a) A = 1,4.10""^ m^/s = SgVg = SiVi (1)
trong đ Sg, Vg, Si, Vi ldn lugt la tilt didn va vdn tdc d mat tiiodng vd d Id day bitọ
Tfi cdng thfic (1), bid’t tilt didn mat thoang va tilt didn Id d day bito, ta tfto dugc vdn tdc tai totog nod đ.
Kit qua la Vg = 17,8.10 ^ m/s ; Vi = 1,4 m/s. v^ - v’^
b) vf - Vg = 2gh, suy ra h =^ 2- « 0,1 m (ldn din nfia bito).
^g
5.9. Cdt rfigu vang cao h (m) tao ra mdt dp sudt btog dp sudt khf quyln. Ta cd :
P = Pa = Pvanggh
Bilt p^ang = 0,984.10^ kg/m^ ; g = 9,8 mii ; p^ = 1,013.10^ N/m^ ; ta tfto dugc h :
h = 10,50 m
5.10. Chilu cao cua cdt thuy ngan d ap sudt tidu chuto la : _ Pa 1,013.10-^
pg 13,59.10^9,8 0,76 m
Chilu cao cua cdt thuy ngto luc sdp cd bao la hi = 0,760 - 0,020 = 0,740 m. Ap suat tuong tog bang : ^ ’ ^ Q I ’ ] ^ -0,74 = 0,986.10^ = 9,86.10^^ Pạ
5.11*. a) Ap dung dinh luat Bec-nu-li cho hai dilm : Pl + 2P^1 = P2 + 2’^^^ + pgh ’ (1)
ttong đ h = 0,5 m la đ chdnh chilu cao gifla hai dilm. Mat khae, ta cd :
ViSi = V2S2 (2)
trong đ Si va S2 la tjlt.didn ngang tai vi tri 1 va vi tri 2. Tfi (2), ta cd :
Sl 0,8 J,.-,
V2 = v i - ^ = v i - j = 4vi (3) ’=»2 0,4
Thay (3)vao(l), taduge :
- p ( v | - v f ) = P i - P 2 - p g h
^p.l5vf = (2,5 - 1,5). 10^ - 10^.10.0,5 2 (10^^-0,5.10’^). 2
v, =
VJ = 0,816 m/s V2 = 4vi = 3,264 m/s b) Luu lugng đng chay btog :
A = 0 , 8 1 6 . 7 r f ^ l = 4,09.10"^ m^/s
5.12. Dd eh’dto dp sudt btog :
16000.9,8 , _ iQAin3po ^ Pd - Pt = 2 40 " " ’
Pd = Pt + 1,96.10^ = 70.10^ + 1,96.10^ = 71,96.10^ Pa
5.13. Do chdto hai mfic thuy ngdn d hai toato btog dp sudt đng, ta cd : 2pv^ = PHggh
V - fcjlgj- 2-13,6.10l9,8.0,05^^^3^^
V P V 1.25
5.14*. Ap dung dito ludt Bec-nu-li cho mdt dilm nam trdn mat thoang va mdt dilm d mieng d’ng xiphdng, ta cd :
pgh = 2pv^ hay V = 72gh
5.15*. F = 7n-2(p^ - p) = 7n-2(p^ - 0,lpa) = 0,9pa7n-2 5 2
Thay sd : p^ = 1,013.10 N/m ; r = 0,3 m vao cdng thfic trdn, ta dugc : F = 25 765 N.
, , ^ 2Ap 2.180 ,^^^^ ,
V « 388 km/h.
5.17. Ap dung cdng thfic (43.1), bai 43 SGK, ta tfto dfige vdn tdc Vj tai tid’t didn S i :
I 2S2AP ^ I 2.0,1^.1500
^^ ~ "y p(Sf - S^) ~ V 1,0.10^(0,2^ -0,1^) ~ ^ ^
Luu lugng nudc trong d’ng đng btog : A = ViSi = 1.0,2 = 0,2m^/s
Hinh 5.8G
5.18. Cdu Ạ 5.19. Cdu D. 5.20. Cdu D.
5.21. -Di dng chfl U thing dtog. - Dd nudc vao d’ng chfl Ụ
- Dd thdm đu vao mdt toato bdn phai dng chfl Ụ - Mat thoang cfia hai toato se chdto Idch,
bdn cd đu se cao hon (Hito 5J8G).
-Ldp bilu thfic tfnh dp sudt tai:
+ Dilm A (mat phto cdch đu va nudc), tacd:pA = Pa + Pighị
+ Dilm B (cung đ cao d nhdnh bdn kia), ta cd : pg = Pa + P2gh2- Vi PA = PB’ suy ra : Pi = P2:j^-
Do hi va h2, bilt P2 se tfto dugc pi (khdi lugng ridng eua đu). 5.22. - D o thcd gian t dl nudc chay đy cdc (dung đng hd).
- Dfing thudc do kfch thudc ede (dutog kfnh trong D va chilu cao h), tfto dung tfch V cua cdc : V = Sih.
- Do dutog kfnh trong d cua vdi nude, tfnh didn tich tilt didn (bdn trong) S2 cua vdi nudc.
- Ta cd V = Sih = vS2t, tii đ vdn tdc nudc chay ra dfige tfto theo edng thfic :
V =
D^h d^t’