1. The problem statement, all variables and given/known data Derive the equation of motion for the system in figure 6.4 using Lagrange's equations 2. Relevant equations m1=.5m m2=m strings are massless and in constant tension Lagrange=T-V 3. The attempt at a solution I currently have the kinetic energy as .5m1y'12 + .5m2y'22 I am confused regarding the potential energy of the system. I understand each mass will have an m*g*y component associated with them but i am unsure how the tension plays into the potential energy. Once i have the potential energy for the system i can take it from there. Any advice would be greatly appreciated, thanks!