Energy density of a vibrating solid (8 points) the density of kinetic energy at a given point in a vibrating solid where m is the mass of a single atom and a is the bond length. the density of potential energy is ()', where is the spring constant of a bond. (a) for some reason, somebody decides to write a wave as u = a sin(kx-wi) instead of in complex exponential form. tell me for which positions/times the potential energy density is larger than the kinetic energy density. it might to remember that the speed of sound is a c/m. (b) now somebody produces a wave of the form u(xt) = a sin kr sinwt. are the kinetic and potential energy always in phase or not? explain.