Which would you expect to have the greatest amount of friction?
a- a smooth surface on a smooth surface
b-a smooth surface on a rough surface
c-a rough surface and air
d-a rough surface on a rough surface

Point charges q1=+2.00μc and q2=−2.00μc are placed at adjacent corners of a square for which the length of each side is 1.50 cm . point a is at the center of the square, and point b is at the empty corner closest to q2. take the electric potential to be zero at a distance far from both charges. part a what is the electric potential at point a due to q1 and q2? express your answer with the appropriate units.