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Homework Help: Before I attempt this next problem on sliding blocks

  1. May 9, 2004 #1
    I'd like to make sure I understand it.
    It reads...
    "Two objects, A and B, are placed in contact with each other on a horizontal, frictionless surface. Object A weighs 1.5kg, and B weighs 2.5kg. If a force of 8.0N is exerted on the surface of object A in contact with B AND on the opposite surface, (1) determine the acceleration of A and B (2) determine the force pushing B."

    Do you think this means 8.0N is applied to both objects A and B simultaneously?
    (I assume "opposite surface" means the side of A opposite to that contacting B.
     
  2. jcsd
  3. May 9, 2004 #2

    arildno

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    I feel for you; I think the textbook writer is much too vague:

    1)
    You write:
    I assume "opposite surface" means the side of A opposite to that contacting B

    I also have that assumption..

    2)
    We now come to the heart of the matter:
    Does there act a force on B equal to 8.0 N simultaneously with the force(s) acting on A?
    This will be true if we ASSUME that the force on A on the contact side, is in fact, generated by B (nothing else makes much sense, I think).
    Then, by Newton's 3.law, an equal, and opposite force acts upon B from A.

    I believe this is what the problem writer is after..
     
  4. May 9, 2004 #3
    Thanks again. Since the surface is frictionless this is what must be meant.
     
  5. May 9, 2004 #4
    (1) its simply using F = ma, u are given F and m = the sum of the other 2

    (2) i think for the second one you have to find the Force via F = ma again, however you have the acceleration and also the mass. not sure tho
     
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