1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Path Coordinates and constant circular acceleration.

  1. Sep 25, 2008 #1
    1. The problem statement, all variables and given/known data

    A top is made to spin by unwinding the string wrapped around it. The string has a length of 0.64m and is wound at a radius of 0.02m (neglect string thickness). The string is pulled such that top spins with a constant angular acceleration of 12 rad/s^2. Determine the velocity and acceleration vectors in path coordinates when the string has completely unwound. Assume that the top starts from rest.

    2. Relevant equations

    a=(tangential acceleration)*[tex]\hat{t}[/tex]+(normal acceleration)*[tex]\hat{n}[/tex]

    v=(magnitude of velocity vector)*[tex]\hat{t}[/tex]
    3. The attempt at a solution

    The string pulls so that 16[tex]\pi[/tex] revolutions occur which is approximately 315.8 radians.

    Tangential acceleration = r*[tex]\alpha[/tex] or (.02m)(12 rad/s^2) (or is this only for constant circular speed situations?)

    I am pretty well lost on this one. Where do I begin?
  2. jcsd
  3. Sep 25, 2008 #2


    User Avatar
    Homework Helper

    First are you sure that it's 16*π is the number of revolutions?

    As to figuring the velocity maybe you can use the usual kinematic equations?

    Vf2 = Vo2 + 2*a*x

    Only V is in radians/s and x is in radians?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook