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Forces with blocks problem

  1. Oct 1, 2009 #1
    1. The problem statement, all variables and given/known data
    Blocks of 1.0, 2.0, and 3.0 kg blocks are lined up on a table (1kg block being on the left, 2kg in the middle, 3kg being on the right). A rightward poiting 12 N force is applied to the leftmost block. What force does the leftmost block exert on the middle one?


    2. Relevant equations

    F=ma
    a= Force applied / (m1 + m2 +m3)
    a= 12N/6k= 2m/s^2

    3. The attempt at a solution
    Ok so this is what I did:

    12N + F(1on2)=(mass of 2nd block)(acceleration)
    12+F(1on2)=(2kg)(2m/s^2)
    F(1on2)=8N, I got this wrong. Did i miss something, or should this force actually be negative.
     
  2. jcsd
  3. Oct 1, 2009 #2

    kuruman

    User Avatar
    Homework Helper
    Gold Member

    You got he acceleration right and that is good.

    The 1 kg block exerts a force on the middle block that is to the right. The 3 kg block exerts a force on the the 2 kg block that is to the left. You don't have that one. Added together these forces are the net force on the 2 kg block.
     
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