2. a. The graph shows a position vs time graph for a mass oscillating on a spring. Estimate the phase constant o. Replace this value Simple harmonic motion of mass on spring N into the expression x = A cos (wt + () and show that the equation is consistent x in meters 0 with the graph. Justify -1 your choice of the sign of o. -2 1 2 3 4 5 6 t in seconds b. At what position(s) is the potential energy (U) of a mass on a spring undergoing simple harmonic motion equal to 1/3 the kinetic energy (K) stored in the spring? Write your answer in terms of the amplitude A. Hint: Use the conservation of mechanical energy, that is, K + U = E for all points of the oscillation. Further hint: at what point is the total energy most easy to calculate