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Applied Force vs. Normal Force

  1. Oct 23, 2011 #1

    Your teacher says, “Any applied force can also be called a normal force.” Discuss the validity of this statement.

    Thanks guys.
  2. jcsd
  3. Oct 23, 2011 #2


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    No, YOU discuss the validity of this statement and ask questions if you are not sure about the validity of any of the points in your discussion. We are not here to do your homework for you.

    Please read the forum rules for posting homework.
  4. Oct 23, 2011 #3
    I think if the object that is acted upon is on the the X-Y plane, for example, then an applied force can't be considered a normal force if the former is in the same plane as the latter. In order for an applied force to be a normal force it has to be on the Z plane.

    Is this right?

    What do you think, guys?
    Last edited: Oct 23, 2011
  5. Oct 24, 2011 #4


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    I may not be following exactly what you're saying, but if I understand it, an example what you are describing would be a circle (a flat disk) in the XY plane. If that's the case, then a normal force could be one that is applied straight onto the disk from the Z direction (I don't understand what you mean by the "Z plane") OR it could be one that is applied normal to the circle from a direction in the XY plane.

    If I've misunderstood the question, please set me straight and I'll have another think.
  6. Oct 24, 2011 #5

    I like Serena

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    Let me put in an observation.

    The "normal" force is the force perpendicular to any surface with which the surface "pushes back".

    Furthermore, if you push against an object, the object pushes back with exactly the same force in the opposite direction (Newton's third law).

    In other words, if you push against an object perpendicular to its surface, the normal force pushes back with the same force but in opposite direction.

    However, if you do not push perpendicular to the surface, this is not true.
  7. Oct 24, 2011 #6


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    Yes, that is exactly what I had in mind. The force towards the edge of the circle WOULD have to be towards the center and I did neglect to state that.

    Do you see any issue w/ my response?
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