1. 2.W=Fscos 3. 4.

12.(1).

(2).:FS,W=FS FS,W=?

3. 1FSW=FS 2FSW=Fscos(FS4.*.1J5.

5.,10900 cos 1.W2= 90 cos =0W=0.

390 1801 cos 0.WF

1.___________________________.F mg f.N:2.____________

2.hf A.0 B. fh C. 2fh D. 4fh C

1.W=FscosFFS2. W=FScosW=W1+W2+W3+3.

1.[ ] A. B. C. D. 2.[ ]

A. B. C. D.

1371. 2.P1372 (3) (4) 5

1P=W/t2P=Fv3:1,?? 2. 1min1t30s

1 W1W=1J/skW1kW=1000W P=Fv

2 FP=FvP=FvcosvtWtPV t0 P=FvcosFvP= Fvcos

3 P=Fvcos

M=3Kg,F=6N,,3:(1)3?3?(2)3?(3)3?

1.5103 Kg 2m/s21.0103N 1[ ] A. 22KW B. 20KW C. 11KW D. 2KW2 W1W2 P1P2[ ] A. W1>W2P1=P2 B. W1=W2P1P2 D. W1P2 AC

3.4m500N22m [ ]A. 1000W B. 500W C. 250W D. 125W4.[ ]A. FVB. Fv C. vFD. Fv

CC

. 1. 23 4

1Fm,sm,,,, F:Amgs/(cos+sin) Bmgs;Cmgscos/(cos+sin). Dmgs/cosE0 F[ Fcos- mg-Fsin ]SGF scos. A.GCE.F

1,,,,,,,:A.F,;B.F,;C.F,; D.F,.21000.5kg20m,:A.2000J B.1000J C.16J D.

2,,___________________,_________ ?

,:A.;B.;C.90;D.

FR,F,,

2mMAB,AB,FB,AB s,F?A?1m,l,,,,?,?

1m,t=0,F,t=t1F: A.F2t1/2m; B.F2t21/2m ; C.F2t1/m; D.F2t21/m.,F,P= F2t1cos2/mtF

1kg30,3s?3s?33s?(g10m/s2):7010.11717.8

1,,4-9?

2

[]60kW,5t,,0.1,:?,0.5m/s2,?[]4-8,,()? ||,a=0F=f=mg vm=P/mg=6.0105/0.1510310=12(m/s). P=Fvm:.a=(F-mg)/m,. F=m(a+ug)=5103(0.5+0.110)=7.5103(N).t,v1,v1=at.v1:P=Fv1. t=P/Fa=6.0104/7.51030.5=16(s)

1.2..3.4.:Ek=mv2/2.5

1,,,

2. .

38104F=ma v22- v12=2as s= v22- v12/2a w=Fs=mav22- v12/2a =1/2m v22 -1/2m v12,F1/2m v2.1/2mv2.Ek

6.1Ek=mv2/2P=mv,P2=2mEk (2, A.,; B.,; C.,; D..21:4,4:1, A.11B.1:4C.4:1D.2:1DC

A.,;B.,;C.,;D.,,.4,m1m2,m1 > m2 ,, A. m2 ;B m1.;C.;D.5m1 m2 ,m1 =4m2 ,,P1:P2= .ADA2:1

1.2..3.4.:Ek=mv2/2.512342

123

1 A. B. C. , . D.,.2,: A B C D

1 2

3W=Ek=Ek-Ek:W,Ek;Ek,,Ek,. W>0Ek2-Ek1>0,Ek2>Ek1W=0Ek2=Ek1at FS=1/2mv221/2mv12 WW=EK2EK1 W=Ek

( ,; ,,; (). W=Ek=Ek2 -Ek1.

2Fms,F,,.1m=5.0103Kg,S=5.3102m,v=60m/s.0.02,?

3H h::

3F,v,3F,,,.

1 ( )A.,,;B.,;C.,; D.,.2,( ) A.,; B.,;C.; D.,.AC

3,,:( )A.; B.; C.; .D..41kg1m,2m/s, __________-.C D

P144 (3) 56

::,,.[1]hm,s,.[]Fs,,,,v=s /t,:W=mv2/2-0=ms2g/4h:m,,ts,v, ,?

[2]4-12,m ,v0,30,: A.mv02/2; B.mv02; C.2mv02/3; D.3mv02/8.,,.

:1.:W=W1+=EK2.11kg5N,10N2m,1m,,?,?

,,,,,,. :mh,,,,?

h1h2 WG=mgh1-mgh2WGmghmghEp=mgh WG=EP1-EP2

1.:.

:,h,Ep=mgh,h,,Ep,,Ep.,.

:.

1,: A.;B.;C.;D..28m,2m,3m100N,(). A.100J;B.700J;C.-100J;D..

2m,200N,0.5m,,(g10m/s2): A.400J; B.200J;C.100J;D.50J.

:,;,.WG=mgh1-mgh2.,WG=mgh.WG=-mgh;,WG=0..: .

1.,,,: A.; B.; C.; D.; E..:2.3.4.5

:

1.E:.:E=Ek+Ep. 2.:

3.::,,,*,,48:

:.:,,.,,,,,.:E1=E2 Ek= -Ep.

1:m,2mab,,,,:A.b,. B. a, C.ab.D ab22m/s2 ( )A. B. C. D.

,:A.;B.;C.;D..

,:A.(); B.;C.,,;D.;:(),()

[],,,.,E1= mv02;,E2=mgh.E1=E2mv2/2=mgh h=5():E1=mv2;h1:E2=mgh1+ mv12/2=2mgh1.:E1=E2, mv2/2=2mgh1. h1=V2/4g =2.5(m).,().:10m/sm,,g=10m/s2:??

P77 12 P79 11

.:;,,;,;,.