For a doubly ionized lithium atom Li2+ (Z = 3), what is the principal quantum number of the state in which the electron has the same total energy as a ground-state electron has in the hydrogen atom?

Aspring is used to stop a 50-kg package which is moving down a 20º incline. the spring has a constant k = 30 kn/m and is held by cables so that it is initially compressed 50 mm. knowing that the velocity of the package is 2 m/s when it is 8 m from the spring and neglecting friction, determine the maximum additional deformation of the spring in bringing the package to rest.