Q.
The acceleration of an electron due to the mutual attraction between the electron and a proton when they are $1.6 \, \mathring{A}$ apart is, $(m_{e} \simeq 9\times 10^{-31}\,kg, e=1.6 \times 10^{-19}C)$
(Take $\frac{1}{4\pi\varepsilon_{0}}=9\times 10^{9}\,Nm^{2}\,C^{-2})$
Solution: