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Homework Help: Interaction Forces

  1. Nov 15, 2006 #1
    Okay i have a physics problem that i really don't get...pliz help me!!

    A 6.0-kg block rests on top of a 7.0-kg, which rests on a horizontal table.

    a What is the force (magnitude and direction) exerted by the 7.0-kg block on the 6.0-kg block?

    i tried using the formula F sub a and b = F sub b and a
    but my book really doesn't explain how to work out the problem...help!

    bWhat is the force (magnitude and direction) exerted by the 6.0-kg block on the 7.0-kg block?
  2. jcsd
  3. Nov 15, 2006 #2

    Doc Al

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    Staff: Mentor

    First, what can you say about those two forces? (Consider Newton's 3rd law.)

    Second, consider all the forces acting on the top block. (What are they? Hint: There are two forces acting.) What must they add up to?
  4. Nov 15, 2006 #3
    I think that its gravity that is acting on the top block but i don't know what else
  5. Nov 15, 2006 #4


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    Staff Emeritus
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    What would happen to the 6kg block if the only force acting was gravity?
  6. Nov 15, 2006 #5
    it would put more force on the table? could the other force be either mass or friction?
  7. Nov 15, 2006 #6

    Doc Al

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    Staff: Mentor

    Since you are asked to find the force that the bottom block exerts on the top block (that's part a), that should tell you something! That's the second force acting on the top block.
  8. Nov 15, 2006 #7
    Its in the table pushing up the bottom block upwards so the other force would be the table
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