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Homework Help: Find velocity of hanging block in a pulley system

  1. Jul 2, 2012 #1
    A pulley is set up on the edge of a desk. A light string connects a 10 kg block laying on the desk to a 4 kg block hanging off the pulley. The only significant friction is with the desk, and the coefficient of kinetic friction is 0.20. Use the law of conservation of energy to find the speed of the system after the hanging block has dropped 1.5 m.

    Wother = ΔKE + ΔUg + ΔUel
    KE = 0.5 * m * v2
    Ug = m*g*y

    in both KE and Ug equations I need to use mass. Do I solve these equations for each of the masses and then add them all together to equal Wother?
  2. jcsd
  3. Jul 2, 2012 #2
    You only need to solve the first equation, W is the work done by friction, and the system would gain kinetic energy but lose gravitational potential energy.
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