Coulomb's Law: Finding the position where the resultant force is ZERO.
F
13
=
1
/
4 π ε
0
q
1
q
3
/
(
x
1
- x
3
)
2
F
23
=
1
/
4 π ε
0
q
2
q
3
/
(
x
2
- x
3
)
2
F
13
= F
23
q
1
=
µC
q
2
=
µC
q
3
=
Negative
Positive
Resultant force on charge
q
3
is zero at,
(x
2
- x
3
)
2
q
1
= (x
1
- x
3
)
2
q
2
(
0 -
x
3
)
2
q
1
= (
4 -
x
3
)
2
q
2
x
3
=
1.519 or -6.319 m
Two solutions,
but only at one, forces are in opposite direction,
as indicated.
16 µC
6 µC
1.52 m
2.48 m
(-)
(q
1
)
F
21
F
31
(q
2
)
F
12
F
32
(q
3
)
F
13
F
23