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-

-

===
+
=⇒+=
π
k7Lf
-
7#9%#BV(<Jj
-
B+Be#9%#
-
B
-
'eBFn
)k7Lfj

#9%@%I#

B-FnBeFn

b

'
9%@%I#f(eFn

$G#77LMeFn6e+cB-+cB

O
+

*

*
6
6

6
-
x∆

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!"#!$%&!#$'&()%#(*+,#("(#-.(&%
'/0/+123
2 2
1 1
( ) ( )
2 2
k
k l m M v v l
m M
∆ = + ⇒ = ∆
+
D-E
$X#9iW>F$G#QR74G"JF*QR74#=78F($G##Z9(Fs
%&&56%‡5$?&56%
&56%K74"HN7O#A7(h$X#9iW:F#f(QR74#\$X#9iW>7$X

π π
∆ = ∆ − ∆ = ∆ − ∆ =
(UW/%&&56%#=7gF&56%K74g@B-3'F$G#;K@&LMB
-@3$G#&:%&56%K8"H#N:9V#Im7R%&"(%74`l)(S&N
I$G##?$X#9i#q<q##AK#N747LM#:$G#

Bn4#ZmH
/S#&H$X#9iW>qQB-'

l&LM"(%74U(s#(Q7^4#
&LMW>W(%:z
+rIFn{ +F-n{ +rIFn{ [+Fn{
 ! W
1 1
0,1 10
mg
l m cm A
k
∆ = = = =
O$X#9i#q<q#U(
-

ñh 1 1 0
( ) 20 15F k l A N P P N= ∆ + = > + =
%7K$X#9i

•&H$X#9iW:&](U(s%&
K($G#D

b

-
∆l
1

0+
-
+
-

-
1

+

∆l
2

P
r
0
P
r
ñh
F
r
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!"#!$%&!#$'&()%#(*+,#("(#-.(&%
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bµ*+

000000a
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j(@&56%WXYN7O#74N7O$G#7O$G#7O#7LM@&56%@uWXY7K



kA
B


(6
Mv
bµ*+

0000000a


(6
Mv
B



(#(B'

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74h/`U($G#F#f(&]$G#9fZ`Lo#9A"(%74U($G#&H
+
EED-F %De cmtx
−=
+
EED'-%D_ cmtx
π
−=

+
EED-F %D_ cmtx
−=
[+
EED'-%De cmtx
π
+=
 3
h/`&56%I

&

B'@BF-
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m
k
=
ω

BF
S(74W(7JU($G#&H6

BF0F-B0FB0
G#U($G#@9fZKZ#9X$

B(#Be

'
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ω
v
x +
B_O#B#A_
ϕ
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B0
rad-F-=⇒
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D
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BF"L?
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-
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@7K74kU(&56%∆&B
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Trích đoạn DÀNH CHO HS ĐẠT ĐIỂM 9+10)
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