Description: This physlet is very similar to the previous one (EFORCEX) - if you haven't looked at that one, please do so now! This physlet extends that one by letting you pick three charges, and the distances along the axis, and even allow you to rescale the axes. (If you only want two charges, set one to zero charge!)
Note : The graphs look much better in 1m, 2m type distances for the charges .. so, if you want to see distances between the charges as say, 0.2 and 0.4 .. why not make them 2 and 4 m .. the graph shape will be the same!
Extra feature .. animation! If you put the test charge somewhere in the system, you can click the RESTART/PLAY button to "release" the test charge from rest - it will be acted upon by the other charges and move toward or away, depending on the net force on the test charge (if it hits one of the charges, there will be a "collision" and the animation will stop). Now, using that RESTART/PLAY button will start the test charge from rest! If you want to pause the motion, and not move the charge, then continue that same motion, use the RESUME FROM PAUSE button. [See, I found that if you move the charge to a new place, you want to start it from rest .. otherwise the applet would keep the old velocity from the pause - which caused weird, non-physical behavior. So, if you move the charge - use the RESTART/PLAY button ... if you just pause the motion, and then want to continue that motion without you adjusting the test charge .. use the RESUME FROM PAUSE.]
Hey, my charge disappeared! If you test charge flies off the screen to either side, or if it collides with one of the fixed charges - use the RESET button to restore the initial configuration.
Credits : Original problem concept authored by Scott Bonham and modified by Wolfgang Christian. Substantially modified by Scott Schneider.