36.
(a) We use Eq. 25-43 with q
1
= q
2
=
−e and r = 2.00 nm:
U = k
q
1
q
2
r
= k
e
2
r
=
8.99
× 10
9 N
·m
2
C
2
(1.60
× 10
−19
C)
2
2.00
× 10
−9
m
= 1.15
× 10
−19
J .
(b) Since U > 0 and U
∝ r
−1
the potential energy U decreases as r increases.
36.
(a) We use Eq. 25-43 with q
1
= q
2
=
−e and r = 2.00 nm:
U = k
q
1
q
2
r
= k
e
2
r
=
8.99
× 10
9 N
·m
2
C
2
(1.60
× 10
−19
C)
2
2.00
× 10
−9
m
= 1.15
× 10
−19
J .
(b) Since U > 0 and U
∝ r
−1
the potential energy U decreases as r increases.