A linear elastic spring is suspended on two extremes and it will stretch under its weight. How can I write down the differential equation for the the equilibrium configuration? And the exact PDE of the oscillations?
The equation of equilibrium can be obtained by using the calculus of variation.The Eulers equation will give the solution where effect of elasticity to be considered.
As presented, I think that the equation is an ODE (not a PDE). Could you please join a figure in order to be sure I understood the problem you want to treat ? Thank you.