Meriam, Kraige & Bolton — Kinetics of Systems of Particles: Problem 4_5

4/5 The system consists of the two smooth spheres, each weighing 3 lb and connected by a light spring, and the two bars of negligible weight hinged freely at their ends and hanging in the vertical plane. The spheres are confined to slide in the smooth horizontal guide. If a horizontal force \( F = 10 \text{ lb} \) is applied to the one bar at the position shown, what is the acceleration of the center \( C \) of the spring? Why does the result not depend on the dimension \( b \)?