Center of Gravity Problem

  1. 1. The problem statement, all variables and given/known data
    A box of negligible mass rests at the left end of a 2.00-m, 25.0-kg plank (see image). The width of the box is 75.0 cm, and sand is to be distributed uniformly throughout it. The center of gravity of the nonuniform plank is 50.0 cm from the right end. What mass of sand should be put into the box so that the plank balances horizontally on a fulcrum placed just below its midpoint?


    2. Relevant equations
    x_cg = (sum of (the masses x position)) / sum of the masses

    3. The attempt at a solution
    m_p = mass of plank
    m_s = mass of sand
    x_cg= (m_p(0)+m_s(0.25))/(25+m_s)
    I don't know what to set the equation of x-cg equal to. Please help.
  2. jcsd
  3. It's equal to whatever position you called the fulcrum
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