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Circular motion of a coin

  • Thread starter Cfem
  • Start date
  • #1
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Homework Statement


A 4.80 g coin is placed 11.0 cm from the center of a turntable. The coin has static and kinetic coefficients of friction with the turntable surface of us = 0.770 and uk = 0.400.

What is the maximum angular velocity with which the turntable can spin without the coin sliding? (In rad/s)

Homework Equations



Ff = FN(u)
Fa = (mv^2)/r

The Attempt at a Solution



I've always been a little foggy on rotational motion, but for this I converted the grams to kilograms and the centimeters to meters, then set the friction equal to the acceleration:

(.0048)(9.8)(.77) = [(.0048)(v^2)]/.11

Which gave me a v of .911 rad/s. I'm not sure what I did wrong/what I'm missing.
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,230
31
the 'v' you get is the linear velocity, you need to use ω=v/r to get the angular velocity.

(Note: I did not check your answer to see if that is what you did, but your response implied that you put 'v' as the angular velocity)
 

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