A coin is placed 12.7 cm from the axis of a rotating turntable of variable speed

Question

A coin is placed 12.7 cm from the axis of a rotating turntable of variable speed. The coefficient of static friction between the coin and the turntable is 0.43. The speed of the turntable is slowly increased until the coin slides off. What is the speed (in rpm) of the turntable when the coin slides off? A coin is placed 12.7 cm from the axis of a rotating turntable of variable speed. The coefficient of static friction between the coin and the turntable is 0.43. The speed of the turntable is slowly increased until the coin slides off. What is the speed (in rpm) of the turntable when the coin slides off? A coin is placed 12.7 cm from the axis of a rotating turntable of variable speed. The coefficient of static friction between the coin and the turntable is 0.43. The speed of the turntable is slowly increased until the coin slides off. What is the speed (in rpm) of the turntable when the coin slides off?

Explanation / Answer

This is a problem involving centripetal acceleration. From Newton’s 2nd law we have:

F = ma(c) = mg
r² = g
= r² / g

The angular velocity () is:

0.43*9.8 = 0.127*²
² = 0.43*9.8/0.127
² = 33.18
= 5.76
For
> 5.76 rev/min the coin will slide off

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