(mp = 1 67 ×
10–27 kg, me = 9 11 × 10–31 kg)
Solution
(a) (i) The electric force between an electron and a proton at a distance
r apart is:
2
2
0
41
e
e
F
r
ε
= −
π
where the negative sign indicates that the force is attractive 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