How can the map be changed so it shows constant acceleration after the object changes direction

i would think klcio3

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.