Một chất điểm dao động điều hoà với phương trình dạng \(x = cos\left( {2\pi t + \frac{\pi }{6}} \right)\left( {cm,{\text{ }}s} \right)\). Lấy ${\pi ^2} = 10$, biểu thức gia tốc tức thời của chất điểm là:

$x = 5cos(2πt – π/2) (cm)$

$x = 5cos(2πt + π/2) (cm)$

$x = 5cos(πt – π/2) (cm)$

$x = 5cos(πt + π/2) (cm)$

${\text{x}} = 16c{\text{os}}\left( {2\pi t - \frac{\pi }{2}} \right)(cm)$

${\text{x}} = 16c{\text{os}}\left( {2\pi t + \frac{\pi }{2}} \right)(cm)$

${\text{x}} = 8c{\text{os}}\left( {2\pi t + \frac{\pi }{2}} \right)(cm)$

${\text{x}} = 8c{\text{os}}\left( {2\pi t - \frac{\pi }{2}} \right)(cm)$

\(\frac{\pi }{2} < \varphi  < \pi \)

$\frac{\pi }{2} < \varphi  < 0$

$ - \pi  < \varphi  <  - \frac{\pi }{2}$ 

$0 < \varphi  < \frac{\pi }{2}$

\(x{\text{ }} = {\text{ }}5\sqrt 2 sin(2\pi t{\text{ }} + \frac{\pi }{4}){\text{ }}cm\)

\(x = 5\cos (2\pi t - \frac{\pi }{6})cm\)

\(x{\text{ }} = {\text{ }}5sin(2\pi t{\text{ }} + \frac{\pi }{4}){\text{ }}cm\)

\(x{\text{ }} = {\text{ }}5\sqrt 2 sin(2\pi t{\text{ }} - \frac{\pi }{6}){\text{ }}cm\)

\(x = 2c{\rm{os}}\left( {\pi t - \frac{\pi }{2}} \right)cm\)

\(x = 4c{\rm{os}}\left( {2\pi t - \frac{\pi }{2}} \right)cm\)

\(x = 2c{\rm{os}}\left( {\pi t + \frac{\pi }{2}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\pi t - \frac{\pi }{2}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\frac{\pi }{3}t - \frac{\pi }{3}} \right)cm\)   

 \(x = 4c{\rm{os}}\left( {\frac{\pi }{3}t + \frac{\pi }{6}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\pi t - \frac{\pi }{6}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\frac{{2\pi }}{3}t - \frac{{5\pi }}{6}} \right)cm\)