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Solve:
Reflect:
At the maximum compression the magnitude of the spring force is twice the weight of the object and the
system is not in equilibrium.
7.54. Set Up:
Use
In part (a), setting
we have
the amount the spring will
stretch. Also, since
In part (b),
where
Solve: (a)
(b)
and
x
must be positive, so
Reflect:
In part (b) there is additional initial energy, so the spring is stretched more.
7.55. Set Up:
Apply
with
and
therefore, the lost mechanical energy is
Solve:
Reflect:
Part of the initial mechanical energy is converted to thermal energy by the negative work done by friction.
We did not use the stopping time in our solution.
7.56. Set Up:
Apply
with
since the otter returns to the same height. Thus,
Solve:
Reflect:
Part of the initial mechanical energy was converted to thermal energy by the negative work done by friction.
7.57. Set Up:
Use
with
and
Conservation of energy thus becomes:
Solve:
Reflect:
In the absence of air resistance an object released from rest has a speed of
after it has fallen
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 Spring '07
 Shoberg
 Force

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