A student draws a free-body diagram for a box moving to the right on a horizontal floor and includes weight downward, normal upward, and a rightward applied force. The student also adds a rightward 'motion' arrow as a force. What is the flaw in the diagram?

• A. Weight should point horizontally because the box is moving horizontally
• B. A free-body diagram must include only acceleration vectors and omit all forces
• C. Velocity or motion direction is not a force and should not appear as an interaction force on the free-body diagram
• D. The normal force should point downward because it opposes upward support from the floor

Answer: (C)