Two tiny metal spheres a and b, mass ma = 5.00 g and mb = 10.0 g, have equal positive charge q = 5.00 μc. the spheres are connected by a massless nonconducting string of length d = 1.00 m, which is much greater than the radii of the spheres.
a. what is the electric potential energy of the system?

At a certain instant after jumping from the airplane a, a skydiver b is in the position shown and has reached a terminal (constant) speed vb = 52 m/s. the airplane has the same constant speed va = 52 m/s, and after a period of level flight is just beginning to follow the circular path shown of radius ρa = 2330 m. (a) determine the velocity and acceleration of the airplane relative to the skydiver. (b) determine the time rate of change of the speed vr of the airplane and the radius of curvature ρr of its path, both as observed by the nonrotating skydiver.