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Homework Help: Finding Tension of String Connecting Two Blocks on a Flat Surface

  1. Oct 4, 2011 #1
    1. The problem statement, all variables and given/known data
    Two blocks mA= 5.0 g and mB= 10.0kg are connected to a string. Both blocks sit on a smooth inclined surface where the angle on the inclined plane is 30.0°. Block A is about block B on the incline. Find the acceleration of the system of two blocks. What is the tension TB in the string.

    2. Relevant equations
    Fa= mA(g) sin θ
    Fb= mBsinθ

    3. The attempt at a solution
    I used an archived thread to attempt to solve this problem, I got the tension to be 0.

    Mass block A= 5.0kg
    Mass block B= 10.0 kg
    mg of block A= 49 N
    mg of block B= 98 kg

    Fa= mg of block A (sin30°) = 24.5 N
    Fb= mg of block B (sin 30°)= 49 N
    First I found the acceleration of the blocks as a whole using the equation ƩFa=m(acceleration of a) : a = 73.5N/15.0kg, so I found acceleration to be 4.9 m/s^2.

    Then I drew separate free body diagrams for each block to solve for the tension.

    Block A Tension = T+ƩFA=ma(acceleration)
    I found the tension to be zero.
    I used the same equation for block B except I subtracted the tension from the force because the tension is acting in a negative x direction.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 5, 2011 #2
    what do you mean by
    "Block A is about block B on the incline". please type the problem in original and with figure if there is any.......is the string attached to a pulley or the wall ?
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