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Homework Help: Find the normal force on an inclined plane.

  1. Dec 18, 2011 #1
    1. The problem statement, all variables and given/known data
    Find the normal force acting on a mass of 5kg on an incline plane of 30 degrees.

    2. Relevant equations
    Fn = mgsin30 or mgcos30 ?

    3. The attempt at a solution
    I'm not sure if I use sin or cos when finding the normal force on an incline. I have trouble visualizing the angle perpendicular to the plane and moving the angles around.
  2. jcsd
  3. Dec 18, 2011 #2


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    Staff Emeritus
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    Homework Helper

    Welcome to Physics Forums.

    If the surface makes an angle θ to the horizontal, then the normal makes the same angle θ from the vertical. Does that help your visualizing?

    If it's still unclear, think about a horizontal surface, so that θ is zero, and answer these questions:

    1. What is the normal force when the surface is horizontal? Draw a force diagram for yourself, if you need to, to figure this out.

    2. Does your answer to (1) agree with mgsin0 or mgcos0?

    Hope that helps!
  4. Dec 19, 2011 #3
    It works with mgsin theta, but when i try to draw it out it doesn't make sense to me.
  5. Dec 19, 2011 #4

    Doc Al

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    Staff: Mentor

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