中考物理压轴题机械效率压轴题

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F2Ḅ᳛1.2W;ট
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=6¹+¼½=50(^+20(^=70(^.ᦑB'()(3)¾mB=84kg,g=10N/kg,ᡠ»ᱥ;BḄ
GB=mBg=84kgx1ON/kg=840N,ᑣ}ᓣᱥ;BsJKḄ
FB=1(GB+GF)=L(840N+60N)33=300N,¸
Ḅ᳛P=180W,¾P=—=^-=Fv,ttᡠ»
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11A.O-lsᑁᙢ☢ᱥ;Ḅ²ᢝ
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F3=40N,ᡠ»,F3=஻(G+G)=40N,ᓽF3=L(100N+G)=40N,33$G=20N,ᵫᵬᙠ0Ø1sᑁ
Fi=30N஺*FᱥẆÝÞᑮᔣCḄ
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F²=6-F=G-3Fi+G=100N-3x30N+20N=30N;ᦑA┯?)(2)ᵫᙠ2Ø3sᑁᱥᒴv3=2.50m/s,ᡠ»
FḄàᵨæCçḄ4V3=3V3=3x2.50m/s=7.5m/s,
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F2=5ON,ᱥxᓣv4h2=1.25m
FḄàᵨæCçḄêëS2=3h2=3xl.25m=3.75m,
Ḅw=F2S2=50NX3.75m=187.5J;ᦑB'(஺

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13WᨵᵨGhGhGJKn=M=80%,WLF2sF3h3F22NঝPᐭঞS>G----------------------=80%,3X-i-(G+100N)o=S>G=400N,ᱥḄTU:m=VP1=P,2■1(G+G'—FE)vi=l(G+100N)V2,33I(400N+100N-FE)x0.4m/s=i(400N+100N)x0.3m/s,33=S>FE=125N,E=Z[᣸gV᣸="^_=---------------------=0.0125m3,PgIX103kg/ro3X10N/kg:ᱥ`@abc[=[᣸=0.01250?,ᱥḄ<>p=—=C------3.2x103kg/m3஺V0.0125m3ᦑeᫀ>3.2x103஺g.ijkl⚪.ᐳ1o⚪F6.ᙠ“qU&'*Ḅ+,ᦔ᳛”Ḅijbs*tuᵨt᪵Ḅ&'xyz᝞|ᵬஹ~ᡠḄ&'*ijqSḄᦪ᝞⊤ᡠ஺ᦪᱥḄ(ᓣh/mF/N%Ḅ+,ᦔ᳛G/Ns/m

14120.110.366.7%230.11.40.371.4%340.11.80.374.1%420.11.50.2(1)⊤ᑁḄ4ijb⊡ᐙḄᦪ66.7%(ᑮ0.1%).¢ᦪᵨ|b~(⌱¤“ᵬ”ᡈ“~”)ᡠḄ&'*qSḄ஺(2)ᑖ᪆¨©1ஹ2ஹ3ijᦪªᑨ¬/⌕®ᜧ&'*Ḅ+,ᦔ᳛°®ᜧᱥḄ(ᙠ1ijbFᡠ²Ḅ³᜜().1J஺(3)stu¶ᵨ·tḄ&'ᡠ*ᡂḄ&'*ᓣtM¹(ᱥKºḕḄ&'*ᐸ+,ᦔ᳛º½Ḅ¾¿ÀᔩÂÃÄᑭᵨ⊡ᐙ)᦮Ḅ⊤bḄᦪÇÈÄḄᑨÉ>0Àᳮᵫ1¨4ḕËÌḄ+,ᦔ᳛ᓾ·t஺=:(1)4ijḄ+,ᦔ᳛>ÎÏ=Ð=2NX0.1mxioo%=66.7%;WLFs1.5NX0.2mᵫ$=▬ªS=s.=P2m2|~bÜÝᱥ(ḄÞᦪ2,ᦑ⌱àyánL=)h0.1m~ã(2)¨©1ஹ2ஹ3ijᦪª$atM&'*ᱥ(ºᜧ&'*Ḅ+,ᦔ᳛ºäJ®ᜧᱥḄ(ª&'*Ḅ+,ᦔ᳛ã᪷1ijᦪª$W=Gh=2Nx0.1m=0.2J;;frWL=Fs=1Nx0.3m=0.3J;ᵫWL³ªS³᜜>W³=\¥L-íᨵ=0.3J-0.2J=0.1J;(3)0À㨩1ஹ4ijᦪª$ᓣ·tḄ(ᱥ1¨4

15ḕËÌḄ+,ᦔ᳛ᓾ·t஺ᦑeᫀ>(1)66.7%;~ã(2)®ᜧᱥḄ(ã0.1;(3)0Àã1¨4ḕËÌḄ+,ᦔ᳛ᓾ·t஺î.=e⚪(ᐳ6o⚪)7.s᫑᫡ñIòᵨ᝞|ᡠḄ&'*ᡭ;óᙠôḄIõ஺#$IõḄö0.16m3,<3.5x103kg/m3,&'*ᔣᒴ%`@ᙠbḄIõKøᙠḄᵫñùḄF=1800N.(0ὃ⇋᥅35Ḅ6g710N/kg)ü:(1)IõḄTUýþᓟ
(2)
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(3)ᓣᑮ☢Ḅ$%Ḅᦔ᳛&᝞()ᓄ+ᑖ᪆./஺12(1)ᵫp=2E56Ḅ782V=pV=3.5xl03kg/m3x0.16m3=560kg;m(2)ᙠ9ᑮḄ:;2F:=pgV᣸=1.0xl()3kg/m3xl0N/kgx().16m3=1600N,9ᑮḄ;2F=G-F:=mg-F:=560kgx1ON/kg-1600N=4000N,ᵫ>5?n=3,ᵫF=L(F+G)56Ḅ;26=1^-F=3x1800N-4000N=1400N,ᔣᒴᙠḄḄᦔ᳛2

16n=^-x100%=♦B*100%=—Six100%=40Q0Mx100%~74.1%;WDFsnF3X1800N(3)E☄G☢ᑮHᐰ☄G☢Ḅ$%᣸JḄKLMN9ᑮḄ:;MN9ᑮḄ;Oᜧ;PḄᨵᵨSOᜧT᜜SVWX)ᵫY5?Ḅᦔ᳛)ᜧ஺Z2(1)Ḅ78560kg;(2)[1400N,ᔣᒴᙠḄᦔ᳛74.1%;(3)ᦔ᳛&)ᜧ\ᵫᦔ᳛Ḅ]^5?ᙠT᜜SX)Ḅ_`aᨵᵨS)ᜧᡠcᨵᵨSᓰDSḄefg)ᜧᓽᦔ᳛)ᜧ஺8.᝞>ᵬᡠjk☢L[0.2m2,l0.2mḄ78ᙳᒴḄnoKᱥKA,qrᙠsᙢ☢uᙢ☢Ḅvw[6xl03pa\—78[80kgḄxyᙠsᙢ☢ᵨ᝞>zᡠjḄ{A|ᑮlᜐ,xᵨᜧN[FiḄ;AclOcm/sḄᒴᓣᙢ☢uxḄᢝ;[Ni,xᒴḄS᳛[P,Ḅᦔ᳛[.xcḄS᳛ᵨᜧN[F2Ḅ;ᱥKBc12.5cm/sḄᒴᓣᙢ☢uxḄᢝ;[N2,Ḅᦔ᳛[92.?Ni:N2=3:4,21]2=16:15.(g10N/kg)2(1)ᱥKAḄ\(2)xḄS᳛P\(3)ᵨᓣBḄᦔ᳛ᓫ஺

1712(1)ᵫp=£=g5?G=pS=6x103PaxO.2m2=1200N,SSᵫG=mg5?AḄ782mA=—=■=120kg,glON/kgAḄ2p=?&=©”——=3000kg/m3;VA0.2m2X0.2m(2)uxᵫs⊝ᩩ62F+N=mxg=80kgxl0N/kg=800N,ᑣ:Ni=800N-Fi,N2=800N-F2,ᵫ⚪¸5?2Ni:N2=3:4,ᑣ24FI-3F=800N-----জ2ᓣᱥKḄS᳛¼P=Fivi=F2V2,162Fi:F=5:4-----ঝ2ᵫজঝ162Fi=500N,F=400N,2xÁḄS᳛2P=Fivi=500Nx0.1m/sx3=150W;(3)ᦔ᳛2n="Æ=Çᵫ⚪¸5?22w=16:15,WD3FhÉ=ÊÇL*X3L=75%;16163F1h163X500NZ2(1)ᱥKAḄ[3OOOkg/m3;(2)xḄS᳛P[150W;(3)ᵨᓣBḄᦔ᳛Ð2[75%஺9.᝞>ᡠj78[70kgḄxyᙠÒÓÔ$ᡭÖᙽØᙠÙkÚḄÛᩞÝ78[5kg.Éxᵨ120NḄ;ḄÞ,

18ÛᩞßØᙠkX஺xàáOᜧ;&Ûᩞâᙠ᦮äᓣ$%Ûᩞåæc0.2m/sḄᒴᓣ஺ᙠÛᩞçᨵ☄G☢èéḄᦔ᳛[m,ÉÛᩞHᐰ☄G☢èêḄᦔ᳛[ᵬë2112=63:65.ìḄ᥅îᙳ5ïᶍXñÛᩞḄpd=2.5xl()3kg/m3,g=iON/kg,:(1)Éxᵨ120NḄ;ÞÒÓᙢ☢uxḄᢝ;[ᜧ\(2)ᙠÛᩞῃóÙkÚôHᐰ☄G☢Ḅ$%ᙢ☢uxḄᢝ;ḄᨬᜧföᨬNfèe\(3)ÉÛᩞ☄G☢èéxÁḄS᳛\(4)YxᵨäᓣᱥḄᨬᜧᦔ᳛஺(÷ᶇ᦮ᦪ)12xḄ;:Gx=01xg=70kgxl0N/kg=700N,Ḅ;2G=m8=51^ú1(^/1^=5(^,û☄G☢Ḅᦔ᳛2Wᨵᵨ1(GÛ-F:)hGÛ-F:T]1=---------------=----------------------------------------------=--------------------------------WD1(GÛ-F:+G)hGÛ-F:+G☄G☢êḄᦔ᳛2Wᨵᵨ2_Gh_GW2©+G)hG+GG-FGÛ=63:65,G-F+GG+GPVg-PVg:஺—I?:65PVg-PVg+50NpVg+50N

19&ÛᙽḄüḄýᐭ6:v=0.04m3,tiÛᙽḄ;2GÛ=mÛg=pÛVÛg=2.5x103kg/m3x10N/kgx0.04m3=1000N,(1)ᙢ☢uxḄᢝ;2F=Gx-F=700N-120N=580N;(2)Ûᩞᙠ9ᑮḄ:;YxḄ;ᨬNᙢ☢uxḄᢝ;ᨬᜧ,Ûᩞ9ᑮḄ:;2F:=pV᣸g=lxl03kg/m3x10N/kgx0.04m3=400N,Fi=L(GÛ+G-F:)(1000N+50N-400N)=i§0_N)333ᙢ☢Ḅᢝ;2-F1=700N-&N=N;FÿGᩞ☢Ḅᨬᜧᙢ☢Ḅᢝᨬ,F2=2(G+G)=(1000N+50N)=350N,O3ᙢ☢Ḅᢝ:F2=G-F2=700N-350N=350N;F1F2=1^-N:350N=29:21;(3)!ᩞ☄#☢$%Fi=2(G+G-F&)=(1000N+50N-400N)33650=N3v=3x0.2m/s=0.6m/s'(Ḅ)᳛P=F1v=-§^Nx0.6m/s=130W;3(4)+ᱥ☄#☢-./01ᑮḄᔣ4Ḅᨬᜧ5F=G=700N,:'+6./Ḅ᥅8ᙳ:;ᶍ=>(Gᱥ+G)

20Gᱥ=3F—G=3x700N-50N=2050N,WWffl_Gh_Gh__G__2050N_^====98%WaFsF3hF33X700N~°°W(1)!ᵨ120NḄ'Z[\ᙢ☢Ḅᢝ5580N;(2)ᙠᩞῃ`abcdᐰ☄#☢Ḅfghᙢ☢ḄᢝḄᨬᜧijᨬi$k529:21;(3)!ᩞ☄#☢$%'(Ḅ)᳛5130W;(4)ᵨmn./0oᓣ+ᱥḄᨬᜧqrᦔ᳛598%஺10.vᵬᡠy5z{|}~ᩞᧇḄqrABnᩨᩚO5ᩨᩚ⊝BZ1ᑮḄᔣ4ḄAZ1ᑮḄᔣ4(⌱"ᜧ”ஹ"”ᡈ”)ᵨᱥḄ+5500N,|}2000NḄᱥᵯᔁq'ḄFᵬ=1600N,¡./0Ḅᦔ᳛nm=62.5%;ᵨ¤᪵Ḅ./ᢥ§v0ᒴ©oᓣª¤Ḅᱥᵯᔁq'Ḅ5F§§./0Ḅᦔ᳛5n§ὃ⇋▭¯°ᑣFᵬ>Fz.,nm>n§(⌱ᡈ=”)஺BJOAAᵬ7,´(1)µ5OAVOB,ᵫFAXOA=FBXOB:¸FA>FB;(2)./0Ḅᦔ᳛1]=fºx100%=100%=_2_x100%=100%W»Fs2F2X1600N=62.5%(3)ᵫvy:¸ᵬvhn=2,§vhn=3,ᵫF=—(G+G):¸Fᵬn>F§᪷¾⚪À:¸Á{ÂÃoᓣᱥÄÅᒴ©oᓣÆǪ¤ᑣᨵᵨ)ª¤É

21Wᨵwᨵ§ÊËÌÍ./◤⌕ÐÑ'+6᥅8ÒḄÓ᜜)ÊËᵫn=—=——-—W»Wᨵ+WÓ:¸,nᵬ§஺ᦑWᫀ562.5%;>;>0H.vᵬzn×ØyÀvÙᵨᵯqÚ./0ÛᱥÜAÝÞaßàáÂᔣᒴ©Ø×â'AḄFiãätåᓄḄvç᝞v§ᡠy஺é¸./»+6X1()3N,AêᓣḄ©Çëì5O.lm/s(gí10N/kg,=>/jîäḄ᥅86'+=ὃ⇋ïðஹñµòḄóô).õ(1)ᱥÜAö☄#☢1ᑮḄ&(2)ᱥÜAdᐰ☢-ᙠêᓣfghᵯqḄ)᳛஺´ᱥÜ÷ᙠhøᒴ©o×F=G-F&ᱥÜ☄#☢F&ùFÊᜧ!ᱥÜdᐰ☄#☢F=G,(1)ᵫvç:¸úÂÜAḄ+GA=2.4x104N,ûdᐰᙠhâ'ᐸ5Fi=1.4X104N,ᡠýúÂÜAö☄#☢1ᑮḄ&F&=6-FI=2.4X104N-1.4xlO4N=1X104N;(2)./0ᨵ4þ'(ÿ
ᱥᐰᵯḄF=L(Gᱥ+G)=lx(2.4xlO4N+6xlO3N)a44=0.75X104N,ᑣFḄv=4x0.1m/s=0.4m/s;ᦑFḄ᳛P=Fv=0.75xl04Nx0.4m/s=3000Wo

22(1)ᱥA!☄#☢%ᑮḄ'(lx1()4N(2)ᱥAᐰ☢,ᙠ.ᓣ012ᵯḄ᳛(3000W஺12.89ᢈ;<=>Ḅ?ᓣᱥḄ@A᝞CᵬᡠF஺C2ᩚCDJKLᩚEHஹDI<ᔠᡂSTUVᙠᙢ☢.஺;XYᙠᙢ☢.Z0[\Ḅ>[\JḄ᥅).(1)F1JF2Ḅ(2)2=?=ᱥA%Ḅ(GA,ᱥB%Ḅ(GB,[\%Ḅ(G.ᒴ?ᓣᱥAcᱥA_[\Ḅ᦮(Ẇv%ᑖ᪆᝞ᵬᡠF஺ᒴ?ᓣᱥBcᱥB_[\Ḅ᦮(Ẇv%ᑖ᪆᝞yᡠF஺ᵫCᵬஹy2F#=GA+G2F2=GB+G(ᱥsḄᵨḄ,

23Ff=Fi,F2'=F2,■_GA+Gᡠc,...(1)¢2GR+GᵫCv£}v52¥ᦻ§1|}P1=2P2,PFX2V222£1_5=:ফ¢2aGR+G..ᵫ(1)ஹ(2)-----ª=Ḃ…(3)GB+G4wᨵ
GAGBᵫT]1°ᓫ=5%,T|l=,H2=...(4)W
AGA+GGB+G°³°—-µ°=5%...¶5·GA+GGB+Gᵫ¶4·ஹ¶5·GAA117-=¹G=GA,6=»613஺G343BWᨵAGG4nூ=———--=---:——=80%஺W
AGA+GGA+—A4A¶DFlJF2Ḅ5:4.(2)2=80%஺