Meriam, Kraige & Bolton — Kinetics of Systems of Particles: Problem 4_79

4/79 Each of the identical steel balls weighs 4 lb and is fastened to the other two by connecting bars of negligible weight and unequal length. In the absence of friction at the supporting horizontal surface, determine the initial acceleration \(\bar{a}\) of the mass center of the assembly when it is subjected to the horizontal force \(F = 20\) lb applied to the supporting ball. The assembly is initially at rest in the vertical plane. Can you show that \(\bar{a}\) is initially horizontal?