A coin is placed on a horizontal phonograph turntable.Let N be the normal force exerted by the turntable on the coin, f be the frictional force exerted by the turntable on the coin, and f_s, _max be the maximum force of the static friction.The speed of the turntable is increased in small steps.If the coin does not slide, then A)N increases, f increases, and f_{s, max} stays the same B)N increases, f increases, and f_{s, max} increases C)f increases and both N and f_{s, max} stay the same D)N, f, and f_{s, max} all stay the same E)N, f, and f_{s, max} all increase

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Quizplus · Accepted Answer

The normal force (N) and the maximum static friction force ($f_{s, \text{max}}$) do not change because they are determined by the mass of the coin and the coefficient of static friction between the coin and the turntable, respectively. The frictional force (f) increases to prevent the coin from sliding as the turntable's speed increases, up to the point where it reaches $f_{s, \text{max}}$.

A Coin Is Placed on a Horizontal Phonograph Turntable