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A 15 kg box sits on a horizontal force.

the coefficient of static fricition between the box and the surface is 0.70. if a force P is exerted on the box at an angle directed 37 degrees below the horizontal, what must be the magnitude of P to get the box moving??

  • Physics -

    force down = 15 * 9.8 + P sin 37
    force horizontal = P cos 37
    0.7 (15 + P sin 37) = P cos 37

  • Physics -

    How can a box sit on a force? Do you mean that it sits on a horizontal surface?

    The vertical force applied to the surface by the box is
    15*g + P*sin37.

    The maximum friction force (which starts it moving) is
    Ff = 0.70(15*g + P*sin37)
    This must equal the horizontal component of P, so
    Pcos37 = 15*g + P*sin37
    P(cos37 - sin37) = 15 g
    P = (15/0.1968)*g = 747 N

  • Physics -

    i mean horizontal surface not horizontal force..sorry..

  • Physics -

    I believe Damon neglected to include a g term when considering the weight of the mass. Otherwise, we agree.

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