Physlet Illustration: Energy of a Vertical Mass/Spring
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A 2-kg mass hangs from a massless spring of spring constant k = 5 N/m.
The spring has an equilibrium (unstretched) length of 13 m. The displacement of
the spring from equilibrium is shown in meters, and the velocity of the mass is shown in m/s. Pull down or
push up on the end of the spring to displace the mass from its initial position, and then push
"Play" to watch it move up and down. Study the
graphs of kinetic energy, gravitational potential energy, spring potential energy, and total energy as functions of
time. Can you verify that these energies are calculated correctly? What can you conclude?
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Hints
- When (where) does the gravitational potential energy have its maximum value? Its
minimum value?
- When (where) does the spring's potential energy have its maximum value? Its
minimum value?
- When (where) does the mass's kinetic energy have its maximum value? Its
minimum value?
- How (why) do each of these types of energy change?
- What should be true, according to the Law of Energy Conservation?
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Reference
See Walker, Section 8-3
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Illustration written by Steve Mellema
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