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FMA-2021-07 · 2021 F = ma (AAPT)

2021 F = ma Exam — Question 7

A point mass slides with speed v on a frictionless horizontal surface between two fixed parallel walls, initially a distance L apart. It bounces between the walls perfectly elastically. You move one of the walls towards the other by a distance 0.01L, with speed 0.0001v. What is the final speed of the point mass?
Source: Question 7, 2021 F = ma Exam, © 2021 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.