A stone is thrown straight down from the edge of a roof, 850 feet above the ground, at a speed of 5 feet per second. A. Remembering that the acceleration due to gravity is -32 feet per second squared, how high is the stone 4 seconds later?

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.