1

VIẾT PHƯƠNG TRÌNH DAO ĐỘNG ĐIỀU HÒA
x = Acos(t + )
Phương pháp: 
 Để tìm ω ta có thể dùng các công thức sau:
 


2
T
(s)
 


2
1

T
f
(Hz)
 Để tìm A ta có thể dùng các công thức sau :
  :
Av .
max



  :
Aa .

2

va
A 

 Để tìm
φ:


x
x(t 0) A.cos
cos

A
v(1 0) A. .sin
v(1 0) A. .sin

  



   

    


    






) cm.
C. 


) cm. D. 


) cm.
Bài 3: 

A. x = -12sin2t cm. B. x = 12sin2t cm.
C. x = 12sin(2t + ) cm. D. x = 12cos2t cm.
Bài 4: 
 
A. x = -6cos4t cm. B. x = 6sin4t cm.
C. x = 6sin(4t -


) cm. D. x = 6cos4t cm.
Bài 5: 


A.  B. 
C. 


) cm. D. -


) cm.
C. 


) cm. D. -


) cm.

3

Bài 9: 
 

A.  B. 


) cm.
C. 


) cm. D. 


) cm.
Bài 10:  

A. x = 5




C.
x = 10.cos 4 t + cm.
3





D.
x = 5 2.cos 4 t cm.
4






Bài 12: 

50 3 cm/s

A. x = 5

cos10t cm. B. x = 10cos 


 cm.
C. x = 10cos 


-

A. x = 2 2cos(5t +


) cm. B. x = 2cos (5t -


) cm.
C. x = 2cos(5t +


) cm. D. x = 2 2cos(5t +


) cm.
Bài 15: 

50 3 cm/s
 
A. x = 10cos 


 cm. B. x = 10cos 


 cm.
C. x = 10cos 




2
 

A. x = 10cos(10t -


) cm. B. x = 5cos(20t -


) cm.
C. x = 10cos(10t) cm. D. x = 10cos(10t + ) cm.
Bài 18: 

2
 
M
0

0
= 5 
A.
x 10cos 2 t
4


  


cm. B. x = 5

  
 
A. x = 5cos(2t -


) cm. B. x = 5cos(2t + ) cm.
C. x = 10cos(t -


) cm. D. x = 5cos(t +


) cm.
Bài 21: 
5 10 
A. 


) cm. B. 


) cm.
C.
x 10cos 2 t
4


  



2

5

D. x = 10cos(100t -


) cm.
Bài 24:  
A. x = 10cos(2t) cm.
B. x = 10cos(2t +


) cm.
C. x = 10cos(2t 


)cm.
D. x = 10cos(2t + ) cm.

Bài 25:                 
x = Acos(t +
A. v = Asin(t) cm/s.
B. v = Asin(t +


) cm/s.
C. v = Asin(t +



) cm
C. x = 4cos(t -
2
3
) cm
D. x = 4cos(t +
2
3
) cm
Bài 28:       -


  

A. x = 50cos(5t +


) cm. B. x = 10cos(5t +


) cm.
C. x = 10cos(5t -


) cm. D. x = 10cos(5t -


) cm.
Bài 29:  
A. x = 8cos(t) cm.

Bài 31: 

A.    


 cm.

B.    


 cm.

C.    


 cm.
D.    


 cm.
Bài 32:  

 = 10.
A. x = 4cos 


 B. x = 4cos 




a

t(s)
2
O
1
2