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Energy Change Bars
Tool: The Energy Change Bars Tool
plots colored bars that display the work done on a body and
the changes in the body's kinetic, gravitational potential
and elastic potential energies since the start of the last
simulation. This tool only plots in Run
mode.
Place
an energy bars tool by first selecting the target body, then
clicking on the Energy Bars button, and finally clicking at
the desired position of the bar graph. You can later
reposition the energy bars tool.
In the energy bars tool's
Properties
Box, you can set:
- Refresh time. How often
the tool redraws the energy bars. The default value is
0.2 sec. The shortest refresh time, 0.1
sec, means the energy bars have the same temporal
resolution as the clock.
However, at such a short refresh time, energy readouts
are difficult to read.
- Show energy readouts.
Controls whether energies are displayed as numbers as
well as bars. Default option is to display the
readouts.
- Minimum mode. Displays
the Energy Bars in a small graph . In
minimum
mode, the Energy Bars tool
never shows energy readouts. See the second
figure below.
- Scale mode. You have
two choices,
auto
mode or
hand
mode. For descriptions of
these two modes and what you need to consider in making
the choice, see Choosing
Scale Mode on the
graph
tool's help page.
- Maximum value.
Hand
mode only: Sets the maximum
energy value displayed by the bars. In
auto
mode, setting this value has
no effect.
- Measure in kJ. Controls
whether energy bars and readouts display energies in
joules (default) or kilojoules.
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The figure to the right
illustrates the layout of the Energy Change Bars
tool. The bar graph displays the energies for the
body
element named
Parent, which is attached to a
vertical
spring.
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Parent is also subject to gravity
and an external
constant force labeled
Child.
The Energy Change Bars tool displays the
name of the body in the title banner. On the left, it shows
the work done on Parent by Child
in red. Work done always sums the contribution
of all non-potential, external forces, including
friction.
On the right, Parent's
kinetic energy is shown in blue; the
gravitational potential energy, in green; and
the elastic potential energy of the spring, in
gray.
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Minimum
mode: The figure to
the right displays the same Energy Bars graph
shown in the figure above.
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