Dynamics Dungeon: FBD Builder
How this connects to AP Physics 1 (Topic 2.2, Forces and Free-Body Diagrams): a free-body diagram shows only the forces acting on the object, drawn from the object. Each force is named by what exerts it on the object (for example, the force of the table on the block). Arrow length shows relative size, so a diagram for an object at rest must show balanced forces. There is no "force of motion" in the direction an object is moving.