Question

Two unequal point charges repel each other with a force of 0.2 newtons when they are 10cm apart . find the force which each exerts on the other when they are (a)1cm apart (b) 5cm apart

Answer 1

Hello!
using Newton Coulomb's law,
\[F =k(q _{1}q _{2} / r ^{2})\]
Substituting values in above equation and finding for product of \[q _{1}q _{2}\]
\[k=9E9Nm ^{2}/C ^{2}\]
\[r=10cm=0.1m\]
\[F=0.2N\]
we finally have,
\[q _{1}q _{2}=2.222E -13C ^{2}\]
Now,

a)
using again this formula,
\[F=k(q _{1}q _{2}/r ^{2})\]
Now substituting values,
\[k=9E9Nm ^{2}/C ^{2}\]
\[r=1cm=0.01m\]
\[q _{1}q _{2}=2.222E -13C ^{2}\]
we finally have,
\[F=19.98N\]

b) Kindly, do this one by yourself.

Regards,
Electronics engineer.