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29 August, 23:44

A box of unknown mass is sliding with an initial speed vi = 5.60 m/s across a horizontal frictionless warehouse floor when it encounters a rough section of flooring d = 2.30 m long. the coefficient of kinetic friction between the rough section of flooring and the box is 0.100. using energy considerations, determine the final speed of the box (in m/s) after sliding across the rough section of flooring.

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  1. 30 August, 00:22
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    We know that the Delta E + W (Work done by non-conservative forces) = 0 (change of energy)

    In here, the non-conservative force is the friction force where f = uN (u = kinetic friction coefficient)

    W = f x d = uNd; N=mg

    Delta E = 1/2 mV^2 - 1/2mVi^2

    umgd + 1/2mV^2 - 1/2mVi^2 = 0 (cancel out the m term)

    This will then give us:

    1/2Vi^2-ugd = 1/2V^2

    V^2 = Vi^2 - 2ugd

    So plugging in our values, will give us:

    V = Sqrt (5.6^2 - 2.3^2)

    =sqrt (26.07)

    = 5.11 m/s
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