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Homework Help: Angular Deceleration Question

  1. Oct 28, 2009 #1
    1. The problem statement, all variables and given/known data

    A bicycle is turned upside down while its
    owner repairs a flat tire. A friend spins the
    other wheel of radius 0.4 m and observes that
    drops of water fly off tangentially. She mea-
    sures the height reached by drops moving ver-
    tically. A drop that breaks loose from the tire
    on one turn rises 36.3 cm above the tangent
    point. A drop that breaks loose on the next
    turn rises 31.6 cm above the tangent point
    (the angular speed of the wheel is decreas-

    Find the angular deceleration of the wheel.
    The acceleration of gravity is 9.8 m/s2 . As-
    sume the angular deceleration is constant.
    Answer in units of rad/s2.

    2. Relevant equations

    Max height = (Vi^2)/2g
    Angular Velocity

    3. The attempt at a solution

    Given what I know I converted units
    36.3 cm to .363m
    31.6 cm to .316m

    Then used max height formula to determine the Vi

    Vi1 = 2.6674 m/s
    Vi2 = 2.4887 m/s

    and with this I can find the time buy using the circumference and the velocities to determine the times.

    T1= .9422s for one complete cycle
    T2= 1.0099s for one complete cycle

    And with this I need to use angular acceleration formula to get this, but here is where I am lost and fell like I am going in wrong direction. Can I get some guidance into what I should do next. I know that I might have to use this to find tangent line which between these two to find acceleration...in this cause deceleration. But I am lost.
  2. jcsd
  3. Oct 28, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Instead of this, which assumes constant speed over the course of each cycle, trying using a different kinematic formula that gives you the acceleration directly.

    How do you convert tangential quantities (distance, speed, acceleration) to angular quantites?
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