You put three identical coins on a turntable at different distances from the cen

Question

You put three identical coins on a turntable at different distances from the center and then turn the motor on. As the turntable speeds up, the outermost coin slides off first, followed by the one at the middle distance, and, finally, when the turntable is going the fastest, the innermost one. Why is this?

A. The weight of the coins causes the turntable to flex downward, so the coin nearest the edge falls off first.
B. For smaller distances from the center, the centripetal acceleration is higher.
C. For greater distances from the center, the centripetal acceleration is higher, so the force of friction becomes unable to hold the coin in place.
D. Because of the way the turntable is made, the coefficient of static friction decreases with distance from the center.

Explanation / Answer

C. Since centripetal acceleration = m2r, it increases for every coin as increases with the speed of the turntable, but at any given the centripetal acceleration is also proportional to r -- so at all times the coin further out has the highest centripetal acceleration.

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