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

Question

shayaan_mustafa · Answer

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.