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Question about friction

  1. Feb 23, 2008 #1
    In my physics book it says: "If there were no applied force (F), then Static friction force will be 0."

    What confuses me is this, what if an object was sitting on a conveyer belt moving at a 30 degree angle, for instance. What causes that object to remain on the conveyer belt? obviously the friction between the object and the belt? Am i mixing up coefficient of friction and static frictional force?

    thanks for your time
     
  2. jcsd
  3. Feb 23, 2008 #2

    arildno

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    Gravity then plays the role of applied force (i.e, a force from somewhere else acting upon the object ALONG the surface).
     
  4. Feb 23, 2008 #3
    yeah but what if you change the material being used for the conveyer belt? Then obviously more variables (besides the weight of the object) are introduced. Let's say that a smoother surface is used. The object will now slide down.
     
  5. Feb 23, 2008 #4

    arildno

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    How does that change gravity from being the "applied" force which was what you were asking about? :confused:
     
  6. Feb 23, 2008 #5

    russ_watters

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    Yes. That's dynamic friction. [response was to shayrgob]
     
    Last edited: Feb 23, 2008
  7. Feb 23, 2008 #6

    arildno

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    An addendum:
    Even if the object slides down, graviry is still to be regarded as the "applied" force.
     
  8. Feb 23, 2008 #7
    wanna elaborate?
     
  9. Feb 23, 2008 #8
    Sorry, Arildno already answered your question. I answered something you did not ask, so I deleted it. What I said is not wrong, its just not addressing your question. (Find out the answer to your question first, before moving on to what I said. I dont want to confuse you).
     
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