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Homework Help: Please help me! resolving forces

  1. Sep 24, 2011 #1
    1. The problem statement, all variables and given/known data
    there is a composite shape (cone with ring attached at open end) total mass 52kg,cone m=22kg, ring=30kg find the 2 forces acting vertically upwards. the shape is lying on its side 21deg from the horizontal.

    2. Relevant equations
    (xtotal x mtotal) = (xcone x mcone) + (xring x mring)
    balance forces ( up=down and left=right)

    3. The attempt at a solution

    find the CG using (xtotal x mtotal) = (xcone x mcone) + (xring x mring)
    resolve forces into verical and horizontal components
    balance forces
    the problem im having is that one force is acting through the centrline at the tip of the cone and the other force is acting at the bottom point of the ring ( see pic)

    please help i am pulling my hair out!

    Attached Files:

  2. jcsd
  3. Sep 24, 2011 #2
    Also consider the torque. What should the total torque around any point be, if the object is at equilibrium? Then you have enough info to find the forces.
  4. Sep 24, 2011 #3
    See my sketch, can you determine distances L_1 and L_2? If so take moments about points A and B and the problem is done?

    Attached Files:

  5. Sep 24, 2011 #4
    Yes, if you have distances L_1 and L_2, the forces can be found by considering the moments about A and B.

    Distances L_1 and L_2 can be found using geometry. The pdf you attached in your original post has all the information needed.
  6. Sep 25, 2011 #5
    thank you very much for your replies,

    for equilibrium: clockwise moments must equal anti clockwise moments

    and because the forces are not perpendicular or parallel to the centreline of the CG the distances L1 and L2 must be the perpendicular distances from the CG to the line of action of the forces.

    i have to basically work out the forces at various angles until the cone is vertical to make sure the forces shown in the diagram do not exceed a certain limit as the object is rotated so the same concept of resolving the forces into components(because of the angle that the object is at) and then taking moments will apply.
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