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Newton's Second law: Pushing the box

  1. Feb 27, 2017 #1
    Can someone please help me solve this question below.

    1. The problem statement, all variables and given/known data

    How much force is needed to push a 20 kg box across a floor at a constant speed of 0.5 m/s [forward] against a frictional resistance of 4 N?

    2. Relevant equations
    Fnet = m.a

    3. The attempt at a solution
    Since the velocity is constant, the acceleration will be 0. If that is correct the net force is going to be 0, which doesnt make any sense.
     
  2. jcsd
  3. Feb 27, 2017 #2

    gneill

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    Staff: Mentor

    Why's that? Did you draw the Free Body Diagram?
     
  4. Feb 27, 2017 #3

    cnh1995

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    Homework Helper

    The "net" force is zero. You are asked to find the force that needs to be "applied" to the box.
     
  5. Feb 27, 2017 #4
    Is there a formula that I can use to find the "applied force"?
     
  6. Feb 27, 2017 #5

    gneill

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    Staff: Mentor

    That's the purpose of this exercise: You're meant to find that formula by analyzing the problem using the given information.

    As already mentioned, you need to draw the FBD to see how the forces combine.
     
  7. Feb 27, 2017 #6
    Is it going to be 4N because the forces have to be balanced?
     
  8. Feb 27, 2017 #7

    cnh1995

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    Yes.
     
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