The
corresponding gravitational force (always attractive) is:
2
p
e
G
m
m
F
G
r
= −
where mp and me are the masses of a proton and an electron
respectively 2
39
0
2 4
10
4
e
G
p
e
F
e
F
εGm m
=
=
×
π
(ii) On similar lines, the ratio of the magnitudes of electric force
to the gravitational force between two protons at a distance r
apart is:
FF
e
Gm m
e
G
p
p
=
=
2
4πε0
 1 3 × 1036
However, it may be mentioned here that the signs of the two forces
are different