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发表于 2019-9-13 23:46:11 | 显示全部楼层 |阅读模式
??????????2.4????????(???)

???? ????????????????????

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1???????????????? ?2????????????????? ?3?????????????????T??????? ?4????????????????????????__________________????????????????________________????????? _____________????????????V0 ?Vt? 5???????????????????1T???2T???3T???????______________________??1T???2T???3T????? _______________??1T???2T???3T?????_____________??????????????____________________? ???????

22

1? v-v0=2ax???

22??? v?v0v?v0v?v01(v?v0)v2?v01222

?a??t????x?v0t?at?x?v0?a??v?v?2ax02 ta2a22aa

?????1??????????50m/s???????????????????4m/s????????????????????????

2

?????????V0=0m/s ?????a=4m/s V=50m/s ??????x??

2

v2?v0

????V-V0=2ax ? x? ???????a???????????

2a

2

2

2

2250?0?????????????x?m?312.5m 2?4

?????1??????????????????????????????????5m/s?????????50m/s????100m????????????????????????????????????????????????????????????????????????????????????

2???????????????

?1????????????????????????

??????????????????????v0??????????vt???????????? vt?v0?at?a?

vt?v0v?vt11vt?v02v0?vt

??x?v0t?at2?x?v0t?t?t?????????x?vt??v?0

t22t22

?????2??????????????5s???????????50m?????????2??

2

???15m/s??????1???????????????

?????????? ??????1?????????v1?????a????????????12 12

??? ??V2=V1+at?15 =V1+5a ? ??x=v1 t ?50=50=5v1+5 ?

22????????V1=5m/s?a=2m/s

2

????????

? ???

?????2????????????????????????????????????????

???????????????60km/h??????????????????????120km/h????????????????

?2??????????????????????????????????????????????Vt/2=V

??????????????????????v0??????????vt?????????????????????????????????C??????Vt ?????

2

v0?vtv0?vt

?vt????v????vt? v

????????????????????????????????????????

?????3??????????????????v0=2.0m/s????3????????4.5m???????????x4.5

????3???4.5m????v?:?3???????v = m/s=4.5m/s

t1????vt?v?v2.5?4.5m/s?a?

2

vt?v04.5?2

??1m/s2t2.5

?????3????????????????5s??????3s?????7.2m??3s?????

16.8m??????????

?3?????????????????????????v0????vt???????????

vs/2?

?????????????????????????v0??????????vt????????C??????

??

?VS2

v0?vt

2

22

?????4?????????4m/s????????A??????????????C????????B???VA:VC=4:3??C?B????2 ?s???? ?1???????????? ?2??????

?????????vA:vC=4:3vC=3m/s

?C??AB????vc=

vA+vB=2vC

222

4

+vB=23

222

vB= m/s ?SBC=

2

????S=SBC=7m

?????4????????????????10m?s???????2m??4m?????????V1 ? V2??v1?v2??

A?1?1B?1?2 C?1?

2 D?1?3

t

????????A???C?B?AC?????????????????????????B??

2t

??vt/2?vx/2????????????? ???????B????vt/2?vx/2????????????

2

vt/2?vx/2

2

?4???????????????????????????????????S=at

????????SI=S1 SII=S2-S1 SIII=S3-S2 12

SI=S1=v0t+ at

2

112322

SII=S2-S1=v0-(v0)=v0

222115222

SIII=S3-S2=v0-v0(2t)-)=v0t+ at

222

?S=SII-SI=SIII-SII==at

2

???????????????????????????????SM-SN=(M-N)at ?????5?????????????????1s???3s?????????2m?4m??? ?1??2?????v2 ?2?3s??????? ????1?????????????????????????????

2

22

SM-SN=(M-N)at S3-S1=(3-1)at=4-2a=1m/s?? S1?2m ??V0.5=

2

S12m

??2m/s???a=1m/s2???v0=1.5m/s??v2=3.5m/s t11s

?2????v3=4.5m/s??? ?2m/s?

?????5?

????????????????????1s?????????1.2m?3.2m????????a??????1s???????v1?v2?v3?

?5??????????????????t??

2

?1s??2s??3s??ns????????S1:S2:S3::Sn=1:4:9::n

??1s???2s???3s???ns??????SI:SII:SIII::SN=1:3:5::(2n-1)??2s???2s???3s????ns????????v1:v2:v3::vn=1:2:3::n

??1m??2m??3m????????1????????????????????

?????6????????????????????????????????????????

2?

1

??????????2.4?????????????????

???? ??

2.4 ????????????????

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1????????????????v

2

?v02?2ax??????????

2?????????????????????????????? 3???????????????????????????????

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???1??????????????????? ????????????? ????????

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???2??????????????????

????????????????????v0?????????????Vt???????????????????V0?Vt

2

??:

???3??????????????

???4????????

?????3 m/s2??????????????6 m/s?????????????????????????(1)?????????????????????????????????????????? (2)??????????????????????????????

1????????????????????????????????????????? (1)????????

(2)?????????????????????????????(??)???????????????????????? 2????????

(1)??A????B???????????x0??A??B????xA?xB?x0??vA?vB.

(2)??A????B???????????x0??????????????xA?xB?x0????vA<v

B.3?????????

(1)?????????????????(2)?????????????(3)????????(?????)??

???

??????

???1??????v1?????????????????S??????????????v2?????

v1?v2???????????????a?????????????a????????

???2????????

?1?1T??2T??3T???nT????????v1?v2?v3??vn?________________

?2?1T??2T??3T???nT???????x1?x2?x3??xn?__________________

?3????T?????T?????T????n?T??????

x??x??x???xn?________________

?4????x??2x??3x???????v1?v2?v3??vn?________________ ?5????x??2x??3x???????????t1?t2?t3??tn?________________ ?6?????????????????t??t??t???tn?________________________

???3????????????????????v2

1=16m/s?????a1=-2m/s????????????????v2=4m?s????a2=1m?s2

???????????????????????????????????????????

??????

1?????x?v2?v20

2a( )

A??????????????? B?????????????? C???????????????

D?????????a?x????????

2?????????????????????????vt????????? ?

A???????? B?2 s????

C???????????????

D??????????40 m?

3???????a?b?????????????t?0???????????????????????????v?t?????????????????????????????? (

)

4.???????Vg

0????????????????????????????????v022

?????????? ? A

v02gBv0gC3v03v

gD02g

5????????v0????????a???????????????????n

????

?????()

2v0v2v2v200022

A.2a(n?1) B.2a(n?1)C.2anD.2a(n?1)2

????????????????????

??????????

???????????v ???t ?????? ????????a??vv1?v0? ????v1?v0?at ?tt

??????????????????t ???v1 ??????????

???

1? ???40km/h ??????????0.6m/s2 ???????10s ??

???????????

2? ???36km/h ?????????????????2s ???????

?????????????

???????????x ???t ???? ???????????????x?

???

1? ???1m/s2 ?????????12s ??????180m ??????

???????

2? ???36km/h ??????????????????????????

??????5m/s2 ??????????????????

???????????x ???v ????

2?????????????????????????v12?v0?2ax v0?v11?t?v0t?at2 22

???

1???????????216km/h ???????????????2m/s2 ?????????????????????


???????1?????????????????????????
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