$u=acos(\omega t-\frac{x}{\lambda}2\pi)$Do đó $omega=7\pi$$\lambda=5cm$$ v=\lambda f=\frac{\omega}{2\pi}\lambda=17,5cm/s$Đáp án A
$u=acos(\omega t-\frac{x}{\lambda}2\pi)$Do đó $
\omega=7\pi$$\lambda=5cm$$ v=\lambda f=\frac{\omega}{2\pi}\lambda=17,5cm/s$Đáp án A