A board of uniform size and composition sits horizontally on a support positioned under its center. The mass of the board is unknown. If there is a 20.0 kg mass is on the right hand end of the board what is the constant of the spring holding the other end of the board if it is stretched .500 m past its equilibrium position?

Why does the equilibrium position of the spring change when a mass is added to the spring? will the mass oscillate around the new equilibrium position of the spring or the previous position without a mass attached to the spring? if the equilibrium position of the spring changes by 20 cm (assuming no initial mass) when a mass is added to the spring with constant 4.9 kg/s^2, what is the mass of the object attached to the spring?