physics

A fulcrum is placed under the center of a uniform 4.00m long, 3.00kg board. Child A has a mass of 42 kg. This child sits on the left end of the board; Child B has a mass of 26kg. Child B sits on the right end of the board. Where should child C (mass 21 kg) sit in order to have the board remain horizontal? What is the force of the fulcrum?

asked by Joe
  1. The torques:

    m(A) •g•2 +(m/2) •g•1 =
    =(m/2) •g•1+m(B) •g•2+m(C) •g•x

    2{m(A)-m(B)}=m(C) •x
    x=2(42-26)/21 = 1.52 (meters)

    posted by Elena

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