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Homework Help: Does the normal always equal weight, if on a non-inclined plane?

  1. May 25, 2009 #1
    1. The problem statement, all variables and given/known data
    Does the normal always equal the weight, if on a non-inclined plane?

    This is just a general question that I have about normal and weight forces... I was wondering because when I'm breaking up the net forces into components, I was wondering if I should always include the normal and weight, even if its on a non-inclined plane.

    Essentially, I'm asking, does the normal=weight on a non-inclined plane if the plane IS NOT frictionless? If the normal=weight, then why do I still need to include it in the sum of the components on the y-axis?

    2. Relevant equations

    3. The attempt at a solution
    Doesn't require a solution, its just a conceptual question
  2. jcsd
  3. May 25, 2009 #2


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    No, the normal force does not always just equal the weight, even on non-inclined planes. Suppose you have a problem where a person is pulling on a box with a rope that is angled at 45 degrees above the horizontal. While the box is not on an inclined plane, the normal force will not in this instance equal the weight. Hopefully this makes sense.
  4. May 25, 2009 #3
    Thanks, that really helps a lot. It also really makes sense, because if the normal=weight even if there was a force applied at an angle to the horizontal, that means that an additional force would be added onto the y-component... and if the normal=weight, then there's nothing to cancel out that vertical force, and the object would accelerate vertically.
  5. May 25, 2009 #4


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