Two identical uniform solid boxes initially at rest on a horizontal
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Energy and Momentum of Rotating Systems · Energy and Momentum of Rotating Systems
Problem
Two identical uniform solid boxes initially at rest on a horizontal, frictionless table are each pushed over the same horizontal distance d by an external horizontal force of the same magnitude F.
• In Trial 1 the force is applied at the center of one box.
• In Trial 2 the force is applied at the top edge of the other box, so the point of application remains at the same height above the table while the box translates.
Throughout each trial, the line of action of the force always remains horizontal and no other external forces do work.
(a) Describe the observable motion of each box at the instant the force is removed. Explain the similarities and differences in their motions.
(b) For each trial, identify every form of mechanical energy that has changed from the start of the push to the instant the force is removed. Justify each choice with reference to the motion you described in part (a).
(c) For Trial 1, express the final translational kinetic energy KT1 of the box in terms of F and d, showing clear reasoning.
(d) For Trial 2, write an energy balance that relates the work done by the force to the translational kinetic energy KT2 and any additional energies you identified. Explain why the translational kinetic energy in Trial 2 is different from KT1 even though F and d are the same.