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Slider Crank Problem

  1. Dec 9, 2009 #1
    I'm having trouble figuring out this problem. I know how to solve the problem if the angular velocity was known but there seem to be too many unknowns to be able to generate graphs. If anyone can offer advice that would be great.
     

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  2. jcsd
  3. Dec 9, 2009 #2

    jamesrc

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    If you know how to solve the problem, you should have an equation for acceleration as a function of theta (you may not know the value of omega, but you know that the angular velocity is a constant). There's no reason you can't plot this function if you scale your y-axis in units of omega^2...
     
  4. Dec 10, 2009 #3
    I'm having trouble figuring this out when I put the y components together the theta gets canceled out and velocity is not linear in this problem and I have no idea where my mistake was
     
  5. Dec 10, 2009 #4

    Mech_Engineer

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    The problem is basically asking you to find two things:

    • Theta at max velocity
    • Theta at min acceleration
    To find these two values, you can just assume a value for omega (angular speed, d/dt of theta) because those values of theta will not change with angular speed. The graphs of velocity and acceleration vs. theta will change in magnitude but not in shape, so I would just assume soemthing for omega that makes calculation easy (like 60 rpm, 2pi rad/s). The problem states that you should assume the angular velocity is constant, which tells me you are meant to assume a constant value for it.

    The piston motion equations should help you find the result:
    http://en.wikipedia.org/wiki/Piston_motion_equations
     
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