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What is the static friction force acting on the object?

  1. Dec 13, 2016 #1
    1. The problem statement, all variables and given/known data
    A block sitting on a flat surface has a us of 0.5. The normal force acting on the block is 10N. If someone pushes the block with a horizontal force of 2N. What is the static friction force acting on the object?

    2. Relevant equations
    F=ma
    fs=usR (less than or equal to)


    3. The attempt at a solution
    I said that since the coefficient of static friction is 0.5, therefore if we multiply it by 10N then we will get 5N, and that is force of static friction. However the answer is incorrect and the correct answer is 2N. Why is that? Isn't 2N the applied force?
     
  2. jcsd
  3. Dec 13, 2016 #2

    cnh1995

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    Homework Helper

    It is the "maximum" possible force of static friction.
    Also, how can the frictional force be more than the applied force when the object is at rest?
     
  4. Dec 14, 2016 #3

    haruspex

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    Gold Member
    2016 Award

    Did you not understand the significance of the "less than or equal to" rider?
     
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