M1 moments

Maths and statistics discussion, revision, exam and homework help.

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  1. najinaji's Avatar
    • Vengeful, Imperial Overlord of The Student Room
    • Location: London
    • Posts: 3,680
    M1 moments
    The question is:

    'A uniform rod AB has length 5m and weight 20N. The rod is resting on supports at points C and D where AC = 2m and BD = 1m.'

    a) Find the magnitudes of the reactions at C and D:

    I found Rc = 15N, Rd = 5N

    b) A particle of weight 12N is placed on the rod at point A. Show that this causes the rod to tilt about C:
    Eventually ended up with 24>10

    c) A second particle of weight 12N is placed on the rod at E to hold it in equilibrium. How far must E be from A?:

    Can't get this one for some reason.
  2. raheem94's Avatar
    • TSR Demigod
    • Posts: 5,512
    Re: M1 moments
    (Original post by najinaji)
    The question is:

    'A uniform rod AB has length 5m and weight 20N. The rod is resting on supports at points C and D where AC = 2m and BD = 1m.'

    a) Find the magnitudes of the reactions at C and D:

    I found Rc = 15N, Rd = 5N

    b) A particle of weight 12N is placed on the rod at point A. Show that this causes the rod to tilt about C:
    Eventually ended up with 24>10

    c) A second particle of weight 12N is placed on the rod at E to hold it in equilibrium. How far must E be from A?:

    Can't get this one for some reason.
    Your part (a) is correct.

    In part (b), you have to show that  R_D is negative.

    Part (c),

    In part (b) it was tilting about C, so now to hold it, we have put added another particle to keep it in equilibrium. Now the rod is just about to tilt to about C, so  R_D equals zero, now resolve about C to find the answer.
    Let AE be  x

    Do i make any sense?
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