I think you can model the beam with the planar mechanical library, using at least 2 rigid bodies connected together with a pivot junction. The connections with the ground can also include pivot junctions, but one of them will relax one degree of freedom, so I suggest a linear annular junction.
The excitation device can be modelled with a force source (since you know the equivalent force) with a varying direction.
This problem looks like a school exercise. Are you a student ?