Intriguing Problems with Static Friction on Stage

K. Rębilas University of Agriculture in Krakow, al. A. Mickiewicza 21, 31-120 Kraków, Poland

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The phenomenon of static friction is demonstrated in some challenging situations. The work-energy theorem and the center-mass equation are elucidated and clearly discerned when used and interpreted in problems with static friction. Especially, it is demonstrated that it is indispensable to refer to thermodynamics to provide a complete and adequate description of some seemingly purely mechanical problems with static friction involved. The static frictional force, although being a zero-work force, is proved to influence energy acquired by a system. Unexpected values and directions of the static frictional forces are shown for some specific cases. Finally, it is explained how static friction plays a crucial role in the working of a store security tag, a device commonly used at clothes shops to prevent theft.

DOI:10.12693/APhysPolA.139.241 topics: static friction, work-energy theorem, security tag