PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
While investigating horizontal motion, a student pushes a 12kg crate across a level floor at constant speed. The student draws the following free-body diagram (FBD) for the crate.
Verbal description of the student’s diagram:
• A central dot represents the crate’s center of mass.
• An arrow labeled “Fg” points straight downward.
• An arrow labeled “FN” points straight upward, opposite Fg.
• An arrow labeled “Fpush” points to the right, parallel to the floor.
• An arrow labeled “fk” points to the left, parallel to the floor.
• An additional arrow labeled “inertia” points to the left, overlapping the friction arrow.
Assume air resistance is negligible.
(a) Identify any forces on the diagram that do not represent real interactions acting on the crate. For each, explain why it should not appear on a proper free-body diagram.
(b) Determine whether any real forces acting on the crate are missing from the diagram or drawn in an incorrect direction. If so, list and justify each one.
(c) Redraw a corrected free-body diagram for the crate. Your diagram should follow standard conventions: a single central dot, one arrow per real force, no force components, and no overlapping arrows. Label each force clearly.
(d) Using your corrected diagram, explain how the forces shown are consistent with the observation that the crate moves at constant speed across the floor.