Dismiss Notice
Join Physics Forums Today!

V = r times omega

  1. Mar 2, 2010 #1
    I do not understand why velocity is equal to the radius times the angular velocity. Angular velocity is given in radians per second. How does this equal velocity when multiplied by the radius?

    Thanks yall! I'm new here by the way.

    2. Relevant equations

    3. The attempt at a solution

  2. jcsd
  3. Mar 2, 2010 #2

    where S is the Arc Length.

    So think of it like r*θ/t
  4. Mar 2, 2010 #3


    User Avatar

    Staff: Mentor

    What is the equation for the diameter of a circle, in terms of the radius? That should help it to make more sense.

    Welcome to the PF, BTW.
  5. Mar 2, 2010 #4


    User Avatar
    Homework Helper

    By definition, s=θr. By definition, w=dθ/dt. That's why ds/dt=r*dθ/dt=r*w=v. Why the definition s=θr, you ask? That's how the radian was defined. It's simple, elegant, and leaves out a pesky constants that clutter up equations.
  6. Mar 2, 2010 #5
    Aha, so s=(theta)(radius) because of the equation circumference = 2 (pi) (r) correct?

    Sorry I'm not sure how to get the symbols yet. I'll figure it out.

Have something to add?