7-3
This presentation is the property of its rightful owner.
Sponsored Links
1 / 55

7-3 动能 动能定理 PowerPoint PPT Presentation


  • 118 Views
  • Uploaded on
  • Presentation posted in: General

7-3 动能 动能定理. 一 . 动能. 1. 物体由于运动而具有的能叫动能.. 2. 动能的大小:. 3. 动能是标量.. 4. 动能是状态量,也是相对量.因为V为瞬时速度,且与参考系的选择有关 , 公式中的速度一般指相对于地面的速度 .. 5. 动能的单位与功的单位相同 ----- 焦耳. 6. 动能与动量大小的关系:. 一个物体的动量发生变化,它的动能不一定变化一个物体的动能发生变化,它的动量一定变化. 合. 二、动能定理. 1. 合外力 所做的功等于物体 动能的变化 , 这个结论叫做动能定理. 2. 动能定理的理解及应用要点 :.

Download Presentation

7-3 动能 动能定理

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


7 3

7-3


7 3

.

1.

2.

3.

4.,

5.-----.

6.


7 3

1.,.

2.:

(1)EK2=1/2mv22EK1=1/2mv12.

(2)EK0EK0


7 3

(3),

(4)

(5)

(6).


7 3

(7)..

(8). .

(9)


7 3

.

1.

2.???.

3.EK1EK2

4.W=EK2-EK1.


7 3

mg

H

f

h

mg

1 n

Hh Hh=?

:

mg(H+h)nmgh=0

H + h= nh

H : h = n - 1


7 3

1F0vv2vF ( )

A.11

B.12

C.13

D.14

C


7 3

A

B

2 1m/s 1kg0.2AA1m B

A. 0.5J B. 2J

C. 2.5J D. 5J

A

:S v mgS=1/2mv2

S=0.25mBv

EK = 1/2 mv2 = 0.511= 0.5J


7 3

2m1m2=12v1v2=21s1s2( )

A.s1s2=12

B.s1s2=11

C.s1s2=21

D.s1s2=41

D


7 3

mABBABEBvA

A

h

v

C

B

3

v2/2g+E/mg

: B,,Cv ,ACh

, AB C

mgh E=1/2mv2

h=v2/2g+E/mg


7 3

3 [ ]

A

B

C

D

A


7 3

mHv1v2

4.

V1

f

H

mg

V2

---

---


7 3

F

V=2m/s

F

h=1m

mg

41kg1m2 m/s [ ]

A C D

A 12J

B 12J

C 2J

D 10 J


7 3

O

m

h

A

B

C

5.mhOBv0CAB=BC ,

mgh1 /2 mv02

W1

ABBCW2

mgh -W1 W2= 0

OB

mgh -W1 2W2= 0 - 1 /2 mv02

OC

W1 =mgh1 /2 mv02


7 3

5hmv[ ]

Amgh

Bmv2/2

Cmgh+mv2/2

Dmv2/2- mgh

D


7 3

6. L ABBCAB =L/3, mCBC

A

L

B

C

,

mgLsin -2/3 mgLcos =0


7 3

6.( )

A

B

C

D

B C


7 3

f

v

v /

f

G

G

7.v080%v?

H=v02/2g


7 3


7 3

8.3m m=1kgv0=2m/s f=2NS ( g=10m/s2 )

f

V0=2m/s

mg

h=3m

---


7 3

7.ABl1 l2 ABAABBAA

l1

l2

B

A


7 3

F

F

v

C

S

A

B

9.32 J,

.

8J

24J

AB

S=1/2a1 t2 =F1 t2 /2m

v=at=F1 t/m

BCA

- S=vt - 1/2 a2 t2 = F1 t 2/m - F2 t2 /2m

F2 =3 F1

ABCA F1S+F2S=32

W1= F1S=8J

W2= F2S=24J


7 3

10.MmL


7 3

,s=s1-s2.,

L


7 3

8.mv0,,(,).L,h,(1)?(2)hh?

(1),L= v0t,,h=at2,t

:F=mgma=


7 3

(2)W=Fh=

h,vt=at=


7 3

11F r 8F r/2 [ ]

A0 B7Fr/2

C4Fr D3Fr/2

D


7 3

9.r1r2 Ek1 E k2 T1 T2 ( )

C

AE k2 Ek1 T2 T1

B E k2 Ek1 T2 T1

CE k2 Ek1 T2 T1

D E k2 Ek1 T2 T1


7 3

F

F

f

m

m

f

S2

S1

m

mF()FW1W2Q1Q2Ek1Ek2W1____W2Q1____Q2Ek1_ ___Ek2(><=)

12.

S1S2

W1 W2

Q=fS

Q1 = Q2

,

EK =F-fS

EK1 EK2


7 3

10dfS[ ]

Afs

Bfsd

Cfd

Dfd

B D

S

d


7 3

13.Mh=0.20mL=1.7mm=0.10Mv0=180m/sv=90m/ss=1.6m

v1mv0= mv+Mv1

v2


7 3

=0.50


7 3

v0

B

A

11 ABAABAA )

(A) BB

(B) B

(C) BA

(D)BA

A C D


7 3

14.M1000 kgL5 m,h1 m0.12800 N.g10 m/s 2

:f

fMg0.12100010N=1200 N

F2800 N1600 N

Ff,fMgsin1200 N100001/5N3200 NF=1600 N


7 3

s

FfsFLfLMgh=0


7 3

12.v=20m/s,=1.3kg/m3,=20m2,P=_________,_____W()

Ek=

P=


7 3

15.1kg5m/s4kg0.022S1m/sg10ms

f1f2

f1t=mvtmv0f1=2 N

flf2tMv,f2m Mg

v05m/s flf2s=Mv2 S=05 m


7 3

13.23

A23 B32 C49 D94

B

Ek=

32


7 3

16.mR7mg,

A.mgR/4 B. mgR/3 C. mgR/2 D.mgR

C

:,v1,

7mgmg=mv12/R

v2,mg=mv22/R

W,:

mg2RW=mv22mv12


7 3

W=mgR/2

(1)

(2)FW=FscosF


7 3

17.ABsBB2sAAABv0BABABA,BAB

:AB

ABv1


7 3

ABv2. mv1=2mv2,

AB,


7 3

14.ABmA6kgmB=3kg3NAABA075 mv=2/3ms

FAB

LAFL=mAv12--------


7 3

TFmAv1mAmBv2-------

AB

F075LmAmBv12

mAmBv22

L025m


7 3

18.mABs =2.88m2m CA CA1=0.22 AB2=0.10 C2mg/5F ABC?


7 3

ABACABABCABABCCAB

lABACf1Af2

1=0.22 2=0.10


7 3

AC,F.

ABmv1=(m+m)v2

s1.

ABf3AB


7 3

C

l=0.3(m)


7 3

19.500t3min45km/h54km/h.(g=10m/s2)

W+W=1/2mv2m-1/2mv2

Pt-fs=1/2mv2m-1/2mv2

F=fvm=P/f

P=600kW.


7 3

15,t,0v.M,P,f..

Ptfs = 1/2 mv2


7 3

16.mv0vmts

A.

B.

C. s/t > (v0+vm) / 2

D.

A C D

: Pt fs =1/2m(vm2 - v02 )

f=F=P/vm


7 3

20.ABBCCDABCDBCmADDAhCDLABBCTNP


7 3

v0StaSat2

v0at

S0= v0t

S02S

f W1=fS=mv02

W0=Fs0=2mv02

Q=mv02


7 3

TW=PT

,W=Nmv02NmghNQ

Lv0TNL


  • Login