=+Problem 1.4 Let us consider the guided double pendulum of Figure 1.14.c where a mass m1 is prescribed to move without friction on a bar making an angle ???? with respect to the vertical direction. The spring of stiffness k is attached to a fixed point and its undeformed length is d0.

Gravity g is acting along y. Using the degrees of freedom s and ????, write the energies of the system and find its equations of motion.