Tension between 2 blocks and friction.

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


    A block of mass m1 = 2 kg and a block of mass m2 = 3 kg are tied together and are pulled from rest across the floor by a force of P = 25 N. The coefficient of friction of the blocks with the floor is µ = 0.14.

    I found the acceleration to be 3.6266 m/s2.

    I need to find the tension in the string between the blocks.

    2. Relevant equations

    F=ma and Ff=u(mg)

    3. The attempt at a solution

    The total frictional force is 6.867 N. m1 has a frictional force of 2.7468 i think, and m2 has a frictional force of 6.7596 i think. I think the pulling force on m1 is 7.2532 N. I mean, i tried creating different summations of the forces, but I don't know what I'm doing wrong. I'm sure I could figure it out, but I need to at least know how to add the forces up in each direction. Thanks so much.
  2. jcsd
  3. PhanthomJay

    PhanthomJay 6,298
    Science Advisor
    Homework Helper
    Gold Member

    Good. You should round it off though to 3.6

    where did you get this?
    how did you arrive at this?
    Draw a Free Body Diagram of block 1 (isolate it) , and examine the forces acting on it to solve for T using Newton 2. What is the acceleration of block 1?
  4. okay, I typed the wrong number in for m2's frictional force. I meant to type in 4.1202 N. I arrived at m1's pulling force by (2)(3.6) = F. Right, I thought I tried creating a FBD but for some reason I'm doing something wrong. Is the acceleration on block m1 = 2.25 m/s2? At this point I am not sure what I am supposed to do.

    EDIT: wait, doesn't the acceleration have to be equal to 3.6m/s2?
    Last edited: Sep 22, 2008
  5. Hey, if someone could help me. I'm really stuck on this one, I just think I've dug myself a deeper hole trying to work this out. I would really appreciate any more help.

    EDIT: I solved it. it's 10 N...
    Last edited: Sep 23, 2008
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