The potential energy of a one-dimensional mass m at a distance r from the origin is: u(r)=uo (r/r ± λ^2 r/r ) for 0 < r < [infinity] , with u0 , r, and λ all positive constants. a. find the equilibrium position r0 . let x be the distance from equilibrium and show that, for small x, the pe has the form u = const +1/2kx^2. what is the angular frequency of small oscillations?