Potential energy in common problems: there are certain systems that show up again and again in physics, because they are useful models for other phenomena. it is thus to store key equations for these systems in long-term memory. look up or figure out the formula for the potential energy u of the following systems: (a) an object of mass m located a distance y above the ground (which we will assume to be at zero potential energy, for convenienc. if it , assume that y is much smaller than the radius of the earth. (b) a spring with stiffness k that has been displaced from equilibrium a distance δ . (c) a pendulum consisting of a mass m attached to a string of length l, and the string has been pulled back from equilibrium through an angle θ. assume that the string is hanging straight down and the potential energy is zero when θ 0. i want the exact formula for the potential energy of this system, not the quadratic approximation! (d) a satellite of mass m located a distance r from the center of the earth. (e) two point charges ı and g2 separated by a distance r.