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Offset slider question

  1. Feb 22, 2017 #1
    • Thread moved from the technical forums, so no Homework Template is shown
    I've been struggling with this question and wondered if anyone could help;
    For the mechanism shown determine for the angle θ = 45°:
    (I) the velocity of the piston relative to the fixed point O (V bo)
    (ii) the angular velocity of AB about point A (Wab)
    iii) the acceleration of point B relative to A (Aba)
    upload_2017-2-22_19-26-20.png

    So far I know that Woa = 300 x 2.pi / 60 = 31.42 rad/s^-1

    then Voa = r Woa = 50x10^-3 x 31.42 =1.57ms^-1

    now I know that I have to use velocity diagrams to calculate Vbo but I'm just confused about how to do it and also how to know what direction each of the velocities are in, this has been stressing me out for a while so any help would be appreciated!
     

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  3. Feb 24, 2017 #2

    haruspex

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    Break the velocity of point A into horizontal and vertical components. How does each of these affect the velocity of B?
     
  4. Feb 27, 2017 #3
    thanks for your reply haruspex, I'm not sure how to break it up into horizontal and vertical components I've really hit a blank!
     
  5. Feb 27, 2017 #4
    I thought that the tangential velocity was the value Voa, the length of the arm multiplied by its angular velocity?
     
  6. Feb 27, 2017 #5

    haruspex

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    You have found the speed, and you know the direction. Do you not know how to find the component of a vector in another direction?
    Niall did all that in the OP. Am I missing something?
     
  7. Feb 27, 2017 #6

    Nidum

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    Ok . Thanks .
     
  8. Feb 28, 2017 #7
    Do you mean using V (vertical) = V Sinθ and V (Horizonal) = V Cosθ to calculate the vertical and horizontal components?
     
  9. Feb 28, 2017 #8

    haruspex

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    Yes.
     
  10. Mar 1, 2017 #9
    So V = 1.57 Sin(45) = 1.11 vertical and]
    V = 1.57 Cos(45) =1.11 Horizontally,

    Assuming that B can only move horizontally then it would have the same velocity as Vao horizontal which = 1.11ms-1, then using this data I could find Wab and the acceleration, am I right in thinking B moves horizontally to A?
     
  11. Mar 1, 2017 #10

    haruspex

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    Yes, its instantaneous motion is just that horizontal component.
     
  12. Mar 1, 2017 #11
    OK I'm starting to get my head around it now thanks a lot for the help!
     
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