Theo mẫu nguyên tử Bo, trong nguyên tử hiđrô, chuy...

D

- Hướng dẫn giải

$\begin{array}{l}
\text { Ta có }{r}_{\mathrm{n}}=\mathrm{n}^{2}{r}_{0} \\
\text { Mà }{F}_{\text {dien }}=\mathrm{F}_{\mathrm{ht}} \Leftrightarrow\left\{\begin{array}{l}
\mathrm{k} \frac{\mathrm{q}_{0}^{2}}{\mathrm{r}_{0}^{2}}=\mathrm{m} \frac{\mathrm{v}^{2}}{\mathrm{r}_{0}} \\
\mathrm{k} \frac{\mathrm{q}_{0}^{2}}{\mathrm{r}_{4}^{2}}=\mathrm{m} \frac{\mathrm{v}_{4}^{2}}{\mathrm{r}_{4}}
\end{array}\right.
\end{array} \Leftrightarrow\left\{\begin{array}{l}
\mathrm{k} \frac{\mathrm{q}_{0}^{2}}{\mathrm{r}_{0}^{2}}=\mathrm{m} \frac{\mathrm{v}^{2}}{\mathrm{r}_{0}} \\
\mathrm{k} \frac{\mathrm{q}_{0}^{2}}{256{r}_{0}^{2}}=\mathrm{m} \frac{\mathrm{v}_{4}^{2}}{16{r}_{0}}
\end{array} \Leftrightarrow 256=\frac{16{v}^{2}}{\mathrm{v}_{4}^{2}} \Rightarrow{v}_{4}=\frac{\mathrm{v}}{4} .\right.. $