*This preview shows
page 1. Sign up
to
view the full content.*

Electrical Energy and Capacitance
43
16.9
(a) Use conservation of energy
()
se
f
i
KE
PE
PE
KE
PE
PE
++
=++
(
or
)
()()
0
KE
PE
PE
∆+
∆ +
∆ =
(
)
0
KE
∆=
since the block is at rest at both beginning and end.
2
max
1
0
2
s
PE
kx
−
max
x
(
,
where
is the maximum stretch of the spring.
)
max
e
PE
W
QE x
−
=
−
Thus,
2
max
max
1
2
kx
QE x
+−
=
00
, giving
( )
( )
65
5
.
0
01
0
Vm
0.500 m
N m
××
=
max
25
0
.
0
C
2
100
QE
x
k
−
==
±
²
±
³
±²±³
±²
(b) At equilibrium,
Σ=
Therefore,
0,
or
0
e
q
FFF
k
xQ
E
− + =
−
+
=
1
0.250 m
2
eq
max
QE
xx
k
=
Note that when the block is released from rest, it overshoots the equilibrium

This is the end of the preview. Sign up
to
access the rest of the document.