will have to check on your first solution, since it doesn't make much sense to me, since the force and the object wont be on the same universe (at least for that small period of time) - feel free to correct me here -
about your second solution, yup, the blackhole is indeed a close definition an ustoppable force (at least per this universe standars), any object capured by the black hole will remain unmmovable in relation to the black hole, but not in relation with the universe thus conserving motion, but the example refers to linear motion (at least I am assuming so), and the act of absorbing it is changing the conditions again. But a solution would be to move the universe (at least to fit the example) making the universe fixed to the unmmovable object, but once the force meets the object, the universe moves, making the force unstoppable and the object unmmovable at the same time...