| Energy Changes Bars Tool: The Energy Changes Bars Tool plots colored bars that display the energy put into an object, the energy put out by th eobject, and the changes in the object's internal energies. 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. View mode. Determines the size of the Energy Changes Bars display. You have three choices, min mode, normal mode, and max mode. The figure at the bottom of this help page illustrates the differences between the three modes. 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.
The figure below illustrates the layout and the three different View modes of the Energy Changes Bars tool. Three body elements of different masses (Brick [8 kg], Book [2 kg], Balloon [0.5 kg]), are being dragged (pulled) along rough surfaces with forces of 50 N.
For each body, the Energy Input to the body by the dragging force is displayed in the top row. The second row displays the Energy Output to the surface by the body due to friction. The third row displays the Energy Changes in System (i.e., in the body) as a result of being subjected to various forces.