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30. The work done by the spring force is given by Eq. 725:
22
1
()
2
s
if
Wk
x
x
=−
.
Since
x
Fk
x
, the slope in Fig. 736 corresponds to the spring constant
k
. Its value is
given by
3
80 N/cm=8.0 10 N/m
k
=×
.
(a) When the block moves from
8.0 cm
i
x
=+
to
5.0 cm
x
, we have
32
2
1
(8.0 10 N/m)[(0.080 m)
(0.050 m) ] 15.6 J 16 J.
2
s
W
−
=
≈
(b) Moving from
i
x
to
x
, we have
2
1
(8.0 10 N/m)[(0.080 m)
( 0.050 m) ] 15.6 J 16 J.
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 Spring '08
 Any
 Physics, Force, Work

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