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Homework Help: Rotational speed

  1. Mar 28, 2007 #1
    1. The problem statement, all variables and given/known data

    As you approach the I-90 exit in your uncle's little red sports car convertible, you happen to notice a cat crossing the road. Not that you have any particular love of cats (especially this one, whose snooty disposition seems to beckon for a game of chicken), but you swerve out of the way, spilling scalding hot coffee all over your new summer duds.

    Unknown to you at the time, the auto mechanic, having had a late night out and consequently being somewhat in a fog, forgot to fasten the lug nuts on one of your uncle's tires.

    Given your velocity on the exit ramp as 2.9 m/s, a tire mass of 10 kg and radius 32 cm;

    Next, the tire cruises up an embankment at an angle θ = 26° above the horizontal for 1 meter before launching across Piranha Lake. What is the velocity vfinal of the tire at the top of the embankment in m/s?

    2. Relevant equations

    Final KE = Initial KE - m*g*h where h = 1m * sinθ.

    3. The attempt at a solution

    so .5*1.024*9.0625+.5*84.1-98sin26

    So KE= 9.4, now how what do i use to find Velocity?
    Last edited: Mar 28, 2007
  2. jcsd
  3. Mar 28, 2007 #2
    What is the problem asking for? I think the front of the matter will be what to do with your new summer duds!
  4. Mar 28, 2007 #3


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    Gold Member

    Kinetic energy = 1/2*mass * speed ^2 + 1/2 * moment of inertia * angular velocity ^ 2

    I think you need to take the rotational energy into account.
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