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Direction of resultant force

  1. Feb 26, 2016 #1
    1. The problem statement, all variables and given/known data
    why the resultant force on blade is acted downwards (toward A)? why shouldnt it be slanted upwards ?
    since the horizontal component of the force acted 2.12kN to the left , and 0.735kN upwards , we would get the resultant force acting slanted upwards , right ?

    2. Relevant equations


    3. The attempt at a solution
     

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  2. jcsd
  3. Feb 26, 2016 #2

    haruspex

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    There is a typo in the Fx equation. The second 12cos60-12 should be 12cos60+12.
    In the final answer, take note of the direction of the arrow. The angle is 19.11 degrees to the centreline (x axis). The "towards A" just means it is clockwise from that centreline.
     
  4. Feb 26, 2016 #3
    the horizontal component of force should be -1.272 N + 2.54 = 1.27N N to the right, whereas the direction and magnitude of vertical force is the same ? then , the direction of resultant of force should be upwards just like the diagram below?
     

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  5. Feb 26, 2016 #4

    haruspex

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    The calculated Fx and Fy are forces on the stream of water. To get the forces on the blade you have to negate both, giving 2.12kN to the right and 0.735kN down.
     
  6. Feb 26, 2016 #5
    isnt that the the resultant force on blade and forecs of steam of water are of same magnitude and same direction
    ?
     
  7. Feb 26, 2016 #6

    haruspex

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    Action and reaction are equal and opposite. The force the blade exerts on the stream of water is equal and opposite to the force the water exerts on the blade.
     
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