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Two Blocks attached by a string, on an incline

  1. Sep 19, 2014 #1
    1. The problem statement, all variables and given/known data
    In the diagram mA is equal to 3.00 kg and mB is equal to 1.07 kg. The angle of the inclined plane is 38.0°

    6sq6bn.png

    (a) Find Acceleration: 6.03 m/s^2 (got this part)
    (b) Find the tension Tb in the connecting string: Not sure
    2. Relevant equations

    (a) a = (F/mA + mB)
    (b) t = mA * a? or mB * a? Not sure

    3. The attempt at a solution

    Obviously my mA * a and mB * a both didn't work, I'm not sure what the formula should be.
     
  2. jcsd
  3. Sep 19, 2014 #2

    Doc Al

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    Staff: Mentor

    What forces act on each block? Draw yourself a free body diagram for one of the masses. Then by applying Newton's 2nd law, you can solve for the tension.
     
  4. Sep 19, 2014 #3
    I'm sorry, but... What?

    The force that acts on each block is gravity, 9.8 * sin theta. That's how I got acceleration.

    T = m(g+a)? But is that mA or mB?
     
  5. Sep 19, 2014 #4

    Doc Al

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    Staff: Mentor

    Right, but you left it out in your two formulas for tension.

    Do this. Pick a block. Doesn't matter which. Then find ∑F for that block. Direction matters: call down the incline positive.
     
  6. Sep 19, 2014 #5
    Woops, sorry. O_O I missed that.

    3 * (9.8 + 6.03) = 47.49

    I don't know what the summation F means. Sum of forces on the block?

    I usually have practice problems so I can play with them until I figure out how to do them, no such luck on this one.
     
  7. Sep 19, 2014 #6

    Doc Al

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    Staff: Mentor

    Yes.

    Did you pick a block? Which one? What forces act on it? What's their sum?
     
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