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Homework Help: Circlar motion

  1. Oct 23, 2009 #1
    1. A computer disk is 8.0 cm in diameter. A reference dot on the edge of the disk is initially located at θ = +45°. The disk accelerates steadily for second, reaching 1480 rpm, then coasts at steady angular velocity for another second. What are the location and speed of the reference dot at t = 1 s?

    2. v=rw

    3. i already got the 6.28 m/s for speed. and i thought since i have speed i can just do v=rw to get w and then draw a diagram to get the area under the curve. After i got the area just use delta theta/ 2pi=revolution. then minus the whole number and take the decimal to divide by 360 then plus 45 right? but appreantly i am wrong
  2. jcsd
  3. Oct 24, 2009 #2

    Andrew Mason

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    We assume it is at rest at t=0 and accelerates until t = 1s at which time its speed [itex]\omege =2960\pi[/itex] rad/sec. To find the angle it covers in that first second, use:

    [tex]\theta = \theta_0 + \omega_0t + \frac{1}{2}\alpha t^2[/itex]

    Last edited: Oct 24, 2009
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