This isn't a specific problem, but it is a concept that appears in several problems. I'll give an example problem that should make clear what I mean. A block rests on a horizontal surface. Ffric≤1 N. What force (applied horizontally) is needed to move the block? My physics professor says 1 N, but I say >1 N, because if you apply a force of exactly 1 N, it will exactly cancel out with friction and there will be no net force. If it is any greater than 1 N, static friction will be overcome and hence a net force will be present. So my question is, to put a block in motion, does the force of friction have to be cancelled(Fapp=Ffric), or overcome(Fapp>Ffric)?