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Pulley problem

  • #2
    Registered Users Posts: 29,563 ✭✭✭✭ Lumen


    Engineers, I need your brains cos mine isn't working. This is a trivial problem for you, but I left school a long time ago.

    The requirement for the following design is to lift a heavy beam perpendicular to its long axis, i.e. without it tilting as it rises. The whole system is effectively acting as a wide pulley block.

    I think that, simplifying using g=10 and ignoring the horizontal component of forces, that

    f = 10,000N = sum(f2,f4,f6,f8,f10)
    t0 = t1 = ...t9 = 1,000N
    f2 = t1+t2 = 2,000N

    So each pulley deals with the same 1/5 of the load, and the tension in all sections of the rope is the same 1/10 of the load (for a point beam of zero length).

    If we consider a non-zero beam length, then as the beam gets longer the tensions increase, because the vertical component of the vector tension is a relatively smaller fraction of the load at the pulley fixture.

    I think that the free beam will rise parallel to the fixed beam. What do you think?

    IMG-20200723-090312.jpg


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