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Urgent Ocr Mechanics 1 Help Needed Please (again) !!! watch

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    HEY ANOTHER PROBLEM HERE, MAJOR REP GIVEN FOR ANY HELPERS !

    7)
    TWO PARTICLES A AND B, OF MASSES O.5kg and M kg RESPECTIVELY, ARE JOINED BY A LIGHT INEXTENSIBLE STRING.

    PARTICLE A RESTS ON A BOARD WHICH IS FIXED AT 10 DEGREES TO THE HORIZONTAL. THE COEFFICIENT OF FRICTION BETWEEN A AND THE BOARD IS 0.15, THE STRING IS PARALLEL TO A LINE OF GREATEST SLOPE OF THE BOARD AND PASSES OVER A SMALL SMOOTH PULLEY AT THE TOP OF THE BOARD. PARTICLE B HANGS VERTICALLY BELOW THE PULLEY.

    THE SYSTEM IS IN EQUILIBRIUM.

    a) Given that A is on the point of sliding up the plane, show that m=0.161, correct to 3dp

    b) Given instead that A is on the point of sliding down the plane, show that m = 0.013, correct to 3dp

    ANY HELP WILL BE MUCH APPRECIATED AND I WILL LEAVE GOOD REP, PLEASE TRY AND HELP ME OUT !
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    If you resolve on A to get the normal contact force:

    R=4.9cos10=4.83N

    Then you can work out Friction Flim=Ru=4.83*0.15=0.724N

    Then resolve on A: T-0.724-4.9sin10=0 T=1.57

    so then you can resolve on B : 1.57-mg=0 m=0.161kg

    hope that makes sense!

    T = tension btw!
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    a)
    draw a force diagram. i cant be bothered to upload one
    R = 0.5gcos10
    F = 0.15*0.5gcos10
    friction acts down slope

    in equilibrium, acceleration is 0
    T = tension in string
    force up slope = force down slope
    Mg = T = F + 0.5gsin10
    M = (0.5gsin10 + 0.15*0.5cos10)/g
    M = 0.161kg

    b)
    friction acts up slope.
    F = 0.15*0.5gcos10
    force down slope = force up slope
    0.5gsin10 = F + Mg
    (0.5gsin10 - 0.15* 0.5gcos10)/g = M
    M = 0.0130kg
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    Oh and good luck with the exam tomorrow! I've got M1 and C3 tomorrow too! :eek:
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    (Original post by fabz)
    Oh and good luck with the exam tomorrow! I've got M1 and C3 tomorrow too! :eek:
    me too gl
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    (Original post by Undry1)
    me too gl
    How do you think you'll do? I've done a few practice papers today and my marks ranged from 89% to 49% for C3!
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    i should be fine i think. done plenty of past papers. unless there's a HARD question i should do ok . (famous last words)
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    Thanks a lot guys, credits on its way as soon as possible
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