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Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semester

  1. Sep 17, 2010 #1
    1. The problem statement, all variables and given/known data
    A uniform bar AB of length l and weight W is hinged to the wall at its end A and supported by means of a string of length a which is tied to the wall as shown. Find the angle [tex]\theta[/tex] that the bar will make with the wall corresponding to the position of equilibrium
    Untitled.jpg

    2. Relevant equations
    Moment = Force X perpendicular distance


    3. The attempt at a solution

    I had tried to find moment about point A. I had resolved W and T (tension in the string BC) into rectangular components. One along the bar and other perpendicular to the bar. along the bar components will not add to the moments at A while the perpendicular components will get multiplied by the distance (For T and W, l and l/2 respectively) and added according to sign convention (anticlock wise rotation as positive and clockwise rotation as negative). but because the angle ABC is getting too bulky (complicated), I don't think I can anyhow end this problem with answer. Need your immediate help.
     
  2. jcsd
  3. Sep 17, 2010 #2
    Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

    More info:

    W acts from the center of the bar.

    angle A = [tex]\theta[/tex]
     
  4. Sep 17, 2010 #3
    Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

    Are you sure there isn't another bit of information?
     
  5. Sep 17, 2010 #4
    Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

    very sure!
     
  6. Sep 17, 2010 #5
    Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

    There isn't enough information to solve the problem. You need to know where 'C' is.
     
  7. Sep 17, 2010 #6
    Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

    In the diagram attached (I hope it does) it shows the 3 forces W RA and RC meeting at the midpoint of the string. The two triangles (G for geometry, and F for forces) should be similar, and there should be enough information to conclude all the dimensions and forces. The only dimension not shown is the horizontal projection of the G triangle, and that is L/2*(cos theta). But there still is not enough information to bring this to completion.
     

    Attached Files:

    Last edited: Sep 18, 2010
  8. Dec 2, 2011 #7
    Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

    I want the solutions of all the problem i.e in this chapter. So please help me in solving the problem of this chapter...
     
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