Question

1910. In hydrogen atom the electrical force of attraction
between the electron and proton is 8.1 x 10-8 N.
Calculate the distance between the electron and the
proton. Given : charge on electron = 1.6 x 10-19 C.​

Answer 1

According to coulomb,s law

f=_k|q1q2|

r^2

now 1.6 x 10-19 C. = k8.1 x 10-8 N./r^2

r^2/k=8.1 x 10-8 N/ 1.6 x 10-19 C

r^2/k

=5×10^11

r^2=8.9875517923(14)×10^9×5×10^11N/C

r=[8.9875517923(14)×(10^9×5×10^11N/C)]^1/2

I am not sure about the value of K there are 3 values in Wikipedia.