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Homework Help: Me with this phy problem, thx

  1. Sep 27, 2004 #1
    plz help me with this phy problem, thx

    In Figure 5-39, a crate of mass m = 210 kg is pushed at constant speed up the frictionless ramp ( = 26.0°) by a horizontal force F.

    http://www.webassign.net/hrw/hrw7_5-39.gif

    What is the magnitude of the force exerted by the ramp on the crate?




    I use m*g to find Fg, and then using Fg*cos⊙(26) to find Fn(normal Force) but I got it wrong, can anybody help me, thx.
     
  2. jcsd
  3. Sep 27, 2004 #2

    Doc Al

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    Staff: Mentor

    The normal force would be [itex]mg cos\theta[/itex] only if there were no horizontal force F. Instead, consider all the forces acting on the crate (I see three) and apply the conditions for equilibrium.
     
  4. Sep 27, 2004 #3
    three? is it Fg, F and Fn?
     
  5. Sep 27, 2004 #4

    Doc Al

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    Staff: Mentor

    That's correct.
     
  6. Sep 27, 2004 #5
    ok, thx Doc Al
     
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