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Homework Help: Inclined Plane Problem

  1. Dec 17, 2007 #1
    [SOLVED] Inclined Plane Problem

    1. The problem statement, all variables and given/known data
    A box is accelerating down an inclined plane at a rate of 2m/s/s. If the plane is angled at 40degrees, what is the mass?


    2. Relevant equations
    a=F net/m


    3. The attempt at a solution
    I have absolutely no idea how to go about solving this problem. I am a newbie to physics and have tried to think of a way to solve this but without other forces i'm lost please help!!
     
  2. jcsd
  3. Dec 17, 2007 #2
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  4. Dec 17, 2007 #3

    Dick

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    It doesn't matter what the mass is. I don't think you've stated the problem correctly. On an inclined plane with a given inclination and value of g, all masses will accelerate at the same rate.
     
    Last edited: Dec 17, 2007
  5. Dec 17, 2007 #4
    Well i don't think I've stated the problem incorrectly, this is possibly my teacher has due to this question came right off my HW assignment.
     
  6. Dec 17, 2007 #5

    Dick

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    Maybe the question is bad, but the force along the plane acting on the object is mg*sin(40). Since F=ma, ma=mg*sin(40). The mass cancels. You can't possibly determine it.
     
  7. Dec 17, 2007 #6
    Hm does that mean that all objects regardless of mass will accelerate at the same speed given that g remains constant as well as the angle?
     
  8. Dec 17, 2007 #7

    Dick

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    Exactly.
     
  9. Dec 17, 2007 #8
    Wait does this mean that the plane is frictionless?
     
    Last edited: Dec 17, 2007
  10. Dec 17, 2007 #9

    Dick

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    If your instructor is prone to trick questions like this, the answer would be yes.
     
  11. Dec 17, 2007 #10
    Thank you very much for the help, also though does this mean that the plane mentioned is frictionless?
     
  12. Dec 17, 2007 #11

    Dick

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    If the plane isn't frictionless all of the relevant forces are still proportional to m, as is the acceleration. m will still cancel. You need some force entering that is not proportional to m to be able to determine it.
     
  13. Dec 17, 2007 #12
    Alright i get it now thanks.:bugeye:
     
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