Meriam, Kraige & Bolton — Kinetics of Systems of Particles: Problem 4_89

4/89 The open-link chain of total length $L$ and of mass $\rho$ per unit length is released from rest at $x = 0$ at the same instant that the platform starts from rest at $y = 0$ and moves vertically up with a constant acceleration $a$. Determine the expression for the total force $R$ exerted on the platform by the chain $t$ seconds after the motion starts.