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Inclined Plane

  1. Jan 6, 2014 #1
    This is driving me nuts. What am I missing?

    Suppose you have an inclined plane with a mass m resting on it. The free body diagram for the mass m has F_grav downward and F_normal perpendicular to the surface of the inclined plane. Thus, by Newton's Second Law, you have:

    F=F_grav+F_norm=ma with the bolded script indicating vectors. Because F_normal=F_grav*cos(α) where α is the angle of the plane's inclination you get

    F_grav+F_norm=F_grav+F_grav*cos(α)=F_grav*(1+cos(α))=ma.

    But this doesn't make any sense! This indicates that, as the inclination of the plane gets lower and lower, the acceleration gets higher. It's obviously a wrong result but I can't, for the life of me, figure out where my mistake is. lol Any help would be greatly appreciated.
     
  2. jcsd
  3. Jan 6, 2014 #2

    tiny-tim

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    hi rexregisanimi! :smile:
    nooo :redface:

    they're not parallel, are they? :biggrin:
     
  4. Jan 6, 2014 #3
    Ah yes. lol Thanks :)
     
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