Consider the pendulum shown in figure 2. Once it is vertical and in equilibrium, a mass m is attached to the end of the bar of length L. The bar+mass system is rigid. This means that the bar does not bend at any angle ?. For any value of ? ?= 0, the spring exerts a restoring force along the bar, which in turn acts upon the mass, that is directly proportional to ? and in a direction that is perpendicular to the bar. The coefficient of proportionality is ?. The pendulum is displaced an angle ?0 from the vertical and released from rest. Moreover, despite the image in the figure consider the size of the spring and themarble to be negligible compared to the length of the bar. That is, at all times the distance between the center of the marble and the center of the spring is L. Finally, consider that the gravitational acceleration due to the Earth, g, is constant.