GV: NGUYEN DUC ANH - 0972 113 246   ng Nai)
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m 9  u hc
( bui hc s 1 )

1 Mt vt nh ng M = 0,9 (kg), g th cng
i c nh. Mt vt nh ng m=0,1 (kg) chuyng theo
ng vi t 0,2
2
n va chm mm vi M. Sau va chm hai v
i trc cy gia
tc trng g=10m/s
2
 
A 4,5 cm B 4 cm C 4
2
cm D 4
3
cm
Gii: Vn tc ca hai vt sau va chm: (M + m)V = mv
> V = 0,02
2
(m/s)
Sau va chm: x
0
=
mg
k
=
k

vi gian t = ng ca h hai v
A. x = 1,08cos(20t + 0,387)cm. B. x = 2cos(20t +
4

)cm.
C. x = 1,57cos(20t + 0,155)cm. D. x = 2cos(20t +
3

)cm
Gii: Vn tc ca vt m khi va ch
v =
gh2

Vn tc v
0
ca h hai vt sau va chm:
(M+m)v
0
= mv > v
0
=
mM
ghm

2

 a h hai v ng ca h
x
0
- 

2
0
x

v

=
2
2
20
12,0
0,01 
= 0,02 m = 2cm
m
M

O
m
h
M
+
GV: NGUYEN DUC ANH - 0972 113 246   ng Nai)
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ng ca h hai vt x = Acos(20t +)
khi t = 0 x = x
0
= A/2 > cos = 0,5 >  =
3


2
0
mv
>
0
v
=
m
W
0
2
= 2
M
W
0
2

Vn tc v ca h hai vt sau va chm:
(M + m) v = mv
0
>
4
5
Mv =
4
1
Mv
0

> v =

0
2
= 0,2W
0
= W
0
 4. 


2


A. 15 cm
B. 20 cm
C. 10 cm
D. 12 cm

Gii: G
O
M

x
m

O

h

2
0
mv
(2)
T 
3
2
v
0
= - 2
2
m/s > V
max
= 2
2
m/s
Tn s ng :
 =
M
k
=
2,0
20
= 10
2
rad/s
 ng : A =

max
V

-
k
mg
=
k
mg
=
100
10.15,0
0,015m = 1,5cm


6 : Mt con lt nm ngang gm v s
c ng v 5cm. Khi M
qua v i ta th nh v
 ng v
A.
25cm
B. 4,25cm C.
32cm
D.
22cm

Gii:
Tn s a con lc:  =
M
k

20
rad/s.

 ng ca h
'
'

v
= 2
5
