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Homework Help: Coefficient of static friction of clothes

  1. Mar 3, 2010 #1
    A top-loading washing machine has a spin cycle that rotates at 8.5 cycles per second. The spinning drub that holds the clothes has a radius of 35 cm.
    What is the linear speed of the clothes?
    ω = (8.5 cycles/s) / (2pi rad) = 53.4 rad/s
    v = ωr = (53.4 rad/s) * (0.35 m ) = 19 m/s

    A damp pair of jeans has a mass of 2.0 kg. What is the magnitude of the normal force acting on the jeans by the wall of the drums as it spins?
    ΣFy = may
    Fn - mg = (mv^2) / (r) = ... = 2083 N

    What is the minimum coefficient of static friction necessary so that the clothes can remain stuck to the middle of the drum wall, and not just slide down to the bottom?

    I got stuck here on the last question.
    I can't seem to figure out what a is in the x direction. My guess is 0, so the static friction is 0?
    But that doesn't sound right. Could someone help me please?
  2. jcsd
  3. Mar 3, 2010 #2


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    yes, looks good!
    not good...
    You seem to be confusing your x and y directions. For the second part, what is the direction of the centipetal acceleration? What is the net force in that direction (normal forces act pependicular to the objects on which they act)?
    For part 3, what is the net force in the vertical direction? What is the acceleration in the vertical direction (friction forces beween two contact surfaces act parallel to the plane of the contact surfaces)?
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