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F = ma (11–17)
Simple Harmonic Motion
FMA-2026-13 · 2026 F = ma (AAPT)

2026 F = ma Exam — Question 13

A block of mass m slides along a surface with a coefficient of kinetic friction µk . The block is confined to move between two walls separated by a distance L. Attached to each wall is an ideal, perfectly elastic spring with a very large force constant k. The block is launched from the midpoint between the walls with an initial speed v0 directed toward one of the springs. It bounces back and forth between the springs, losing speed only due to friction with the surface. Assume the time spent in contact with the springs is negligible compared to the travel time between them. Which of the following expressions correctly gives the total time T required for the block to come to a permanent rest?
Source: Question 13, 2026 F = ma Exam, © 2026 American Association of Physics Teachers (AAPT) and the U.S. Physics Team. Adapted by PhysicsTrainer: reformatted into a separate question and answer choices for online multiple-choice practice; any shared setup from nearby questions is repeated here. Not affiliated with or endorsed by AAPT or the U.S. Physics Team.