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Applied Maths Statics Question

  • 07-07-2014 9:40am
    #1
    japester
    Registered Users, Registered Users 2 Posts: 100 ✭✭


    Hi there, I've been attempting some old Applied Maths Leaving Cert papers and I've come across a question that has me completely stumped. There doesn't seem to be any solutions for statics questions on thephysicsteacher.ie site either so I'm doubly goosed :-) If anyone could take a look at the question and outline the solution I'd be more than grateful. The question is as follows:


    A uniform rod of mass 2 kg and of length 6y metres, leans against the smooth edge of a rectangular block of mass 6 kg and height 0.8 y metres.
    The rod is smoothly hinged at p to a rough horizontal floor and the block also rests on the floor (see diagram - I can't appear to add images to the post so hopefully there is sufficient info in the question to make it out - actually, the question can also be viewed from the thephysicsteacher.ie website by going to exammaterialappliedmaths.html and just clicking on the 1987 link, going to Q7 on the paper).

    The block is on the point of slipping when the rod makes an angle A with the horizontal, where tan A = 4/3 .

    (i) Show in separate diagrams the forces acting on the rid and on the block.
    (ii) Show that the coefficient of friction between the block and floor is 6/17
    (iii) Find, correct to the nearest Newton, the magnitude of the reaction at the hinge.

    thanks in advance for any help with this question


Comments

  • #2
    japester
    Registered Users, Registered Users 2 Posts: 100 ✭✭japester


    Just figured it out there :-) My problem was that I was treating the normal reactions at the point of contact between the rod and the block as being different forces and not twigging that they are the same value by Newton's Third Law. Many thanks to anyone who was trying to answer the question though.


  • #3
    mcratsix
    Registered Users, Registered Users 2 Posts: 192 ✭✭mcratsix


    japester wrote: »
    Just figured it out there :-) My problem was that I was treating the normal reactions at the point of contact between the rod and the block as being different forces and not twigging that they are the same value by Newton's Third Law. Many thanks to anyone who was trying to answer the question though.

    always hated statics, I found them the hardest of the 9 q's I covered by a distance. Maybe that's just me though


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