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Homework Help: Circular motions

  1. Jun 26, 2004 #1
    I haven't worked with circular motions yet but i have these questions for lab. Could someone please help?

    A group of students observes that a wooden block o mass o.29kg on a string makes 15 rotations in 23.5 seconds at a radius of 0.70 meters. (a) the blocks tangential velocity is.. (b) the blocks angular velocity is..

    I tried using the equation v= 2pi r/T but that's not working. With that I got 0.87m/s but it's not right. What equations should I use for these?
  2. jcsd
  3. Jun 26, 2004 #2
    Hi, I think I got it but do check my work.

    First we calculate the [tex]\omega[/tex] and then we use it to find [tex]v[/tex].

    [tex]\omega = \frac {15 \text{rev}}{23.5 \text{s}} \times \frac {2\pi}{1 \text{rev}} = 4.01 \text{rad/s}[/tex]

    Using [tex]v=r \omega[/tex] we get [tex]v=2.807 \text{m/s}[/tex]
    Last edited: Jun 26, 2004
  4. Jun 26, 2004 #3
    thank you...that's right. I wasn't accounting for the 15 revolutions. I was just using one revolution.
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