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    Two weights P and Q hang in equilibrium from a string which passes over a rough circular cylinder in a plane perpendicular to the axis, which is horizontal. If P is on the point of descending, what weight may be added to Q without causing it to descend?
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    What is the coefficient of friction?
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    just µ
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    Let W be the weight that is added at Q. Then

    P = Q exp(pi*mu)
    Q + W = P exp(pi*mu)

    W
    = P[exp(pi*mu) - exp(-pi*mu)]
    = Q[exp(2pi*mu) - 1]

    (I'm not sure whether the question wants us to express W in terms of P or in terms of Q.)
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    (Original post by Jonny W)
    Let W be the weight that is added at Q. Then

    P = Q exp(pi*mu)
    Q + W = P exp(pi*mu)

    W
    = P[exp(pi*mu) - exp(-pi*mu)]
    = Q[exp(2pi*mu) - 1]

    (I'm not sure whether the question wants us to express W in terms of P or in terms of Q.)
    thanks i was confused about which way to express W also, i thought that i had perhaps missed something obvious, but expressing both ways is probably best just to make sure both are covered! thanks
 
 
 
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