Two boxes are connected by a light rope on a rough horizontal floor. A student treats both boxes and the connecting rope as one system. Which forces should be included when finding the resultant external horizontal force on this system?
The applied pull and rope tension, excluding all floor friction forces.
Floor friction and both rope tensions, excluding the applied pull.
The applied pull, floor friction and both internal rope tensions.
The applied pull and floor friction, excluding forces within the rope-box system.