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A 2 kg block is pushed 2 m along a fixed horizontal surface by a horizontal force of 20 N. The coefficient of kinetic friction of the surface is µk= 0.40.
(a) How much work is done by the 20 N force?
(b) what is the work done by the friction force?
(c) What is the total work done by the net force on the object?

  • physics -

    Wb = mg = 2kg * 9.8N/kg = 19.6N. = Weight of block.

    Fb = 19.6N. @ 0deg. = Force of block.
    Fp = 19.6sin(0) = 0 = Force parallel to
    surface.
    Fv = 19.6cos(0) = 19.6N. = Force perpendicular o surface.

    Ff = u*Fv = 0.4 * 19.6N. = 7.84N. = Force of friction.

    a. W = Fap * d = 20 * 2 = 40J.

    b. W = Ff * d = 7.84 * 2 = 15.68J.

    c. Fn = Fap - Fp - Ff,
    Fn = 20 - 0 - 7.84 = 12.16N.

    W = Fn * d =12.16 * 2 = 24.32J.

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