Chapter 5.1, Problem 14E

5.1.1 Spring/Mass systems: Free Undamped Motion

A certain mass stretches one spring $\frac{1}{3}$ foot and another spring $\frac{1}{2}$ foot. The two springs are then attached in parallel to a common rigid support in the manner shown in Figure 5.1.5. The first mass is set aside, and a mass weighing 8 pounds is attached to the double-spring arrangement, and the system is set in motion. If the period of motion is π/15 second, determine how much the first mass weighs.