Một vật dao động điều hòa theo phương trình $x=10cos[10\pi t+\frac{\pi}{6}] [cm]$. Gốc thời gian được chọn là lúc vật đi qua vị trí có li độ
A. $x=5\sqrt{3}cm$ theo chiều âm của trục tọa độ.
B. $x=-5\sqrt{3}cm$ theo chiều âm của trục tọa độ.
C. $x=5\sqrt{3}cm$ theo chiều dương của trục tọa độ.
D. $x=-5\sqrt{3}cm$ theo chiều dương của trục tọa độ.
Đáp án và lời giải
Đáp án:A
Lời giải:- Thay t = 0 vào phương trình của li độ: $x=5\sqrt{3}cm$. - Vì $\varphi$ thuộc hai góc phần tư phía trên nên $sin\varphi>0$, do đó v < 0, vật chuyển động theo chiều âm.
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