Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Easy angular velocity question

  1. Nov 14, 2011 #1
    1. The problem statement, all variables and given/known data

    A solid disk with a radius of 1.4cm is a rest. The disk has 2.0m of string wound on to its circumference. The string is pulled off the disk by a constant force in a time of 7.3s. What is the final angular velocity of this disk?


    2. Relevant equations

    v = r*ω

    3. The attempt at a solution

    The correct answer is 39.1 rad/s but I keep getting half of that (19.6 rad/sec).

    Since ω = v/r, I solve for v:

    2m/7.3 sec = 0.274 m/s

    then ω = (0.274 m/s)/(0.014 m) = 19.6.

    what am I doing wrong? the correct answer is 39.1
     
  2. jcsd
  3. Nov 14, 2011 #2
    Does a constant force mean you have constant velocity or acceleration?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook