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Homework Help: Linear Speed/Rotational Speed

  1. Feb 2, 2004 #1
    I can define both terms Linear Speed, Rotational speed,

    but I need to find the formula difference so I can show how

    rotational speed is changed to linear Speed.

    I can not find the formula for either.
     
  2. jcsd
  3. Feb 2, 2004 #2

    Doc Al

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    Staff: Mentor

    I assume you are talking about how to find the tangential speed (V) of something that is rotating about a point at some angular speed (ω, measured in radians/sec). The relationship is V=ωr, where r is the distance to the axis of rotation.
     
  4. Feb 2, 2004 #3

    HallsofIvy

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    Science Advisor

    If the angular speed is ω, measured in radians per second, that means that in 1 second, the "wheel" will turn through ω radians. On a "wheel" of radius r, one radian angle cuts an arc of length r*1= r on the circumference of the wheel (remember that the full circle is 2π radians and the entire circumference is 2πr).
    That is, in one second there is a revolution of ω radians which carries a point on the circumference a distance rω.
    Angular speed ω corresponds to a linear speed of v= rω, just as Doc Al said.
     
  5. Feb 3, 2004 #4
    Thanks to all.
    I now understand
    v=w*r
    v= linear speed
    w= Rotational Speed
    r=radius
     
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