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Homework Help: Question about normal friction and acceleration

  1. Oct 5, 2008 #1
    1. The problem statement, all variables and given/known data
    A 60 kg box which in turn pushes a 30 kg box move on wheels so friction is eliminated. The push is 30 N horizontially

    2. Relevant equations
    What is the acceration on the system of boxes and what is Normal friction of the 60 kg box on the 30 kg box?

    3. The attempt at a solutionThe normal friction is 9.8 x60 but I don't know if normal friction can only be hortizontal.
  2. jcsd
  3. Oct 5, 2008 #2
    Anyone out there
  4. Apr 23, 2009 #3
    Hi. I have a question. A body is lying on a slope. We increase the slope until the body starts to move. So my question is, if we stop increasing the slope when the body starts to move will de body maintain constant speed going down, or may it accelerate until it reaches the bottom?
  5. Apr 23, 2009 #4


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    You (or the problem) are using the wrong terms. The problem states there is no friction (between the boxes and the floor), and it should be asking what is the normal force (the horizontal force that one box exerts on the other perpendicular to (normal to) their surfaces in contact with each other) between the two. The force you have calculated is the normal force of the floor on the 60 kg box. What you want is the normal force between the 2 boxes. Are you at all familiar with Free Body Diagrams?
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