Lagrangian Dynamics problem -- need help with setup Here's the problem: A simple pendulum of length b and bob with mass m is attached to a massless support moving horizontally with constant acceleration a. Determine the equations of motion. For the pendulum, x = b sin theta and y = b cos theta (Which of these equations should I use? y = b cos theta?) For the support, x = (v0)t +.5a*t^2 - b sin theta? Is this correct? Kinetic energy is 1/2 m (x'^2+y'^2), correct? Potential energy is U=mgy. If my equations are wrong, could someone tell me why and how to correct them? Your help is greatly appreciated!!!