Coulomb's Law

Set the charge values to 1 and 4 (it doesn't matter which is which) and adjust the position of the charges so that they are one unit apart in distance (located on the x-axis at 1 and 2, for example). Note the force. (a) How does the force compare when one of the charges is moved to make their separation twice as large? (b) Three times as large?

Keeping the charge values as 1 and 4, place one charge at the origin. (a) Find four easy locations of the other charge result in a force of 0.25. (You should be able to find integer values for your answers; express the answers as (x,y) coordinates.) (b) What is the relationship between the x and y coordinates of all the locations that result in a force of 0.25, even non-integer values? (c) Why are the answers to (a) and (b) the same even if you use charge values of 2 and 2?

GeoGebra doesn't have an easy way to show whether the charges are attracted or repelled, and (for some reason) it doesn't show the positive or negative sign in the label the force, but the bar moving above and below the axis does represent the sign of the force. So test it out with different values of charge. What should our physics interpretation be when the force drops below the x axis in this diagram? How does that fit with Coulomb's law?