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Calculate the Kinetic Frictional Force

  1. Jan 22, 2017 #1
    • Member warned to use the homework template for posts in the homework sections of PF.
    The alarm at a fire station rings and a 71.3-kg fireman, starting from rest, slides down a pole to the floor below (a distance of 3.63 m). Just before landing, his speed is 1.42 m/s. What is the magnitude of the kinetic frictional force exerted on the fireman as he slides down the pole?

    m = 71.3 kg
    d = 3.63 m
    Vf = 1.42 m/s

    d = Vf(t)/2
    a = Vf/t
    F = ma

    3.63 m = 1.42 m/s (t) /2
    7.26 m = 1.42 m/s (t)
    t = 5.113 s

    a =1.42 m/s /5.113 s
    a = .278 m/s^2

    F = 71.3 kg (.278 m/s^2)
    F = 19.8 N

    But that's not the answer
  2. jcsd
  3. Jan 22, 2017 #2


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    Homework Helper
    Gold Member

    I didn't check your calculations but the force you have calculated is the "net force" on the fireman's body. You are asked to find the frictional force.
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