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22 March, 07:06

a 2.4*10^2 N force is pulling an 85 kg refrigerator across a horizontal surface. the force acts at an angle of 20.0 above the surface. the coefficient of kinetic friction is. 200, and the refrigerator moves a distance of 8.00 m. find (a) the work dont by the pulling force, and (b) the work done by the kinetic frictional force

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  1. 22 March, 07:37
    0
    a) 1800 Joules

    b) - 1201.47Joules

    Explanation:

    Workdone by pulling force = F (cos angle) * s

    Where s = displacement

    W = 240N (cos20°) * 8m

    W = 1800 Joules

    b) The frictional force will be opposite the displacement, therefore the angle will be 180°

    Workdone by kinetic frictional force Fs=Fn * coefficient of kinetic friction

    W = [ (85*9.8) - 240sin20°) ] * [0.200cos180*8]

    W = (833-82.08) * (-1.6)

    W = 750.92 * (-1.6)

    W=-1201.47Joules
  2. 22 March, 08:27
    0
    a) The work done by pulling force, W = 1804.21 joules

    b) The work done by the kinetic frictional force is, w = 1332.8 J

    Explanation:

    Given,

    The pulling force, Fₐ = 2.4 x 10² newton

    The mass of the refrigerator, m = 85 Kg

    The angle of pulling force acting to the surface, ∅ = 20°

    The coefficient of kinetic friction is, μₓ = 0.200

    The distance covered by the refrigerator, s = 8 m

    The force acting in the direction parallel to the surface is given by

    F = Fₐ cos∅

    ∴ F = 2.4 x 10² x cos 20°

    =225.53 N

    The work done by the pulling force is given by

    W = F · S

    = 225.53 N x 8 m

    = 1804.21 joules

    The work done by the pulling force, W = 1804.21 joules

    The kinetic friction force is given by the formula

    Fₓ = μₓ · η

    Where

    μₓ - coeficient of kinetic frictoin

    η - Normal force, (mg)

    ∴ Fₓ = 0.200 x 85 x 9.8

    = 166.6 N

    The work done by the kinetic frictional force is given by

    w = Fₓ · S

    = 166.6 N x 8 m

    = 1332.8 J

    Hence, the work done by the kinetic frictional force is, w = 1332.8 J
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