physique 1bac cours_03 travail et energie cinetique(autosaved)
TRANSCRIPT
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03
::::
.
.
. :
- .
- .
.
----1111 ::::
1111----1111 ::::
.
21
2cE mv=
m
kgv
m/s
Ec
J.
2222----1111 ::::
Mi im iv:
21
2ci i i
E m v=.
Mi i iOM r=.
Mi i iv r=.
Mi.2 2 2 2 21 1 1
( ( ) ) ( ) ( )2 2 2
i i i i i i i i iEc m r m r Ec m r = = =
:=i
2
i iJ m r = :21
2c
E J
=
J . .
:kg.m2
-2 ::::
1111----1111 ::::
1-1-1 :
.
1-1-2 :
m=400g
40ms = . 1/1:
ivur
irO
Mi(mi)
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zB
zA
zi
0
z
Pur
M5
M
M1
M2
M3
M4
M6
M7
M8
M9
=20ms
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:
M11M10M9M8M7M6M5M4M3M2M1M0Mi
zi(cm)
1 12
i ii
M Mv
+= (ms-1)
21( )
2i iEc mv J=
mgzi (J)
( )i i
Ec f mgz=.
1-1-3
:
( )i iEc f mgz= . AB
:
( )
B A B A
B A B A
Ec Ec mgz mgz
Ec Ec mg z z
=
=
AB:
( ) ( )
( ) ( )
A B A B
A B B A
W P mg z z
W P mg z z
=
=
ur
ur
)-(
Oz
.
:( )B A A BEc Ec W P =ur
.
1-2 ::::
m=600g .
:
Pur
Rur
F P R= +ur ur ur
(. 1(
Fur
puur
F.ur
.
F D
( 2(. :
0 0T P R F T + + = + =ur ur ur r ur ur r
:F T=.
TF .
20ms =.
D
Pur
Rur
T
ur
Pur
Rur
1
2
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1v2v :BA
20 2
31,50.10 3,75 /
2 2 20.10A
M M mv m ss
= = =
2
4 6
3
5,5.1013,75 /
2 2 20.10B
M M mv m s
s
= = =
AB:
2 2
3 2 3 2
1 1
2 2
1 1.600.10 .(13,75) .600.10 .(3,75)
2 2
c B A B AE Ec Ec mv mv
= =
=
52,5cE J =
F:F=7,3 N. F .
Fur
B:WA F AB= ur uuur
-2W=7,3 7.10 51,5J =
:( )B A A BEc Ec W F =ur
F P R= +ur ur ur
.
1-3
:::: ::::
( )B A A BEc Ec W P =ur
( ) ( )A B A BW F W P =ur ur
( )B A A BEc Ec W F = ur
.
:( )B A A BEc Ec W F =ur
( ) ( )
( ) ( ) ( )
A B A B
A B A B A B
W F W F
W F W P W R
=
= +
ur ur
ur ur ur
( )B A A BEc Ec W F = ur
.
AAAABBBB
::::2 2
1 1( ) ( )
2 2ext ext B A A B B A A B
Ec Ec W F mv mv W F
= =ur ur
)1()2(:
2 2
2 1 1 2 2 1 1 2
1 1( ) ( )
2 2ext ext Ec Ec W F J J W F
= =
ur ur
21 .
.
.
: .
M1 M5M0 M2 M3 M4 M6
A B