The force exerted on an object by a nonlinear spring isF = –[k(r – r0) + q(r – r0)3]er,whe...

The force exerted on an object by a nonlinear spring is

F = –[k(r – r0) + q(r – r0)3]er,

where k and q are constants and r0 is the unstretched length of the spring Determine the potential energy of the spring in terms of its stretch .S = r – r0.