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Homework Help: Friction and acceleration

  1. Nov 4, 2007 #1
    1. The problem statement, all variables and given/known data
    Assuming ideal frictionless conditions what is the acceleration of the system if (a)m1=.25kg, m2=.50kg, and m3=.25kg and (b)m1=.35kg, m2=.15kg, and m3=.50kg. This is a picture of a table with m3 on the table, m1 and m2 hanging on the sides.

    2. Relevant equations

    3. The attempt at a solution
    I did a=Fnet/m=9.8N/m1+m2+m3=9.8m/s
    The Fnet's (ma) for a and b both totaled 9.8N. I'm not sure.
  2. jcsd
  3. Nov 4, 2007 #2


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    Homework Helper

    9.8 N is not Fnet. There are forces acting in more than one direction here. You must consider the tensions in the strings connecting the masses in addition to gravity. Draw a free body diagram of each mass, labelling all of the forces. Then use Newton's second law to sum up the forces in each direction for each mass. This will give you a system of equations to work with to solve for acceleration.

    See http://hyperphysics.phy-astr.gsu.edu/hbase/hpul.html#c1 for examples using Newton's second law.
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