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Homework Help: Calculate acceleration of the 4 kilogram block

  1. Jan 25, 2010 #1
    1. The problem statement, all variables and given/known data

    Three blocks of masses 1.0, 2.0, and 4.0 kilograms are connected by mass less strings, one of which passes over a frictionless pulley of negligible mass, as shown above. Calculate each of the following.
    a. The acceleration of the 4 kilogram block
    b. The tension in the string supporting the 4 kilogram block
    c. The tension in the string connected to the l kilogram block

    (Sorry but I cant seem to get the pic on here- basically on one side of the pulley is a 4kg mass, and on the other side is a 2kg mass that is connected by a string to a 1kg mass)

    I don't really know where or how to start. I know I'll need to use Newton's Second Law. But I'm have difficult applying it to these problems.

    Thank you
  2. jcsd
  3. Jan 26, 2010 #2


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    Homework Helper

    Re: Pulleys

    Three masses are connected by two stings.
    All the masses move with the same acceleration.
    Let tension in the string connecting 4 kg and 3 kg be T1, and tension in the string connecting 2 kg and 1 kg be T2.
    For 4 kg, 4*g - T1 = 4*a.
    Similarly write the other two equations for 2 kg and 1 kg. Then solve the equations to find T1, T2 and a.
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