I definitely agree that this card needs to be improved. The “force of gravity” on an object is same no matter what its sitting on, if anything!
Rather than a cloze hint, I would suggest asking for the perpendicular component specifically. E.g.,
For an object on an inclined plane, give the equation for the gravitational force perpendicular to the surface:
{{c1::Fg = mgcos(θ)}}
agree with neheller