https://phet.colorado.edu/en/asimulations/efield

Now remove all charges and add the following charges: a charge of magnitude +1.III|I of mass l.[i and another charge of magnitude 1.II| of mass 1.3. Do these charges attract or repel? In the simulation, it may be helpful to hold on charge static to watch ifthe other charge will continuously move near the static charge. [Hint: ifthey collide a lot, they exert an attractive force on one another; similarly, if they do not collide often, they exert a repelling force on one another.] Next remove all charges and add the following charges: two charges of magnitude +1.0 and of mass 1.11 Do these charges attract or repel? In the simulation, it may be helpful to hold on charge static to watch if the other charge will continuously move near the static charge or you can add more charges of the same magnitude to observe the forces that the charges exert on one another. Lastly, remove all charges and add the following charges: two charges of magnitude 1.D and of mass 1D. Do these charges attract or repel? In the simulation, it may be helpful to hold on charge static to watch ifthe other charge will continuously move near the static charge or you can add more charges of the same magnitude to observe the forces that the charges exert on one another