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Physics

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A 4000N block is moved up a slope that is 20 degrees to the horizontal. If the coefficient of friction is 0.3, find the force parallel to the slope to: a) move the load up the slope b) prevent the load from sliding back

  • Physics - ,

    W=mg= 4000 or do i multiply this by 9.81

  • Physics - ,

    mg=4000 N is correct.
    θ=20°
    μ=0.3 (assumed static friction)

    Gravity force along plane
    F=mg sin(θ)

    Friction force along inclined plane
    =μmg cos(θ)
    direction acts against movement.

    To move load up slope:
    Force required
    =mg sin(θ)+μmg cos(θ)


    To move load down slope:
    Force required
    =μmg cos(θ)-mg sin(θ)
    if μmg cos(θ) > mg sin(θ)
    =0 otherwise

  • Physics - ,

    F=4000sin(20)= 1368.1
    FF= 0.3*4000cos(20)= 1127.6
    FR= 4000sin(20) + 0.3*4000cos(20)= 2495.7
    So 2495.7 N required to move it up the slope
    1127.6 N is required to prevent the load from sliding back

  • Physics - ,

    Downward force due to gravity is
    F=1368.1

    Friction force resisting movement is
    FF=1127.6

    Therefore net downward force
    =force required to prevent load from sliding down
    =F-FF
    =1368.1-1127.6
    =240.45 N

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