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Moments / torque etc ( gravity is considered ? )

  1. Aug 15, 2010 #1
    The whole point is whether gravitational pull is taken account in moments ?

    1. The problem statement, all variables and given/known data
    The apparatus below is set up on Earth. It shows a piece of soft iron X of mass 0.6kg fixed on one end of a uniform beam AB which is pivoted at its midpoint. X is prevented from being pulled down by a fixed magnet by a load of 1.00 kg hunt at A.

    The experiment is now conducted on the Moon where the acceleration due to gravity is 1/6 of Earth. The mass of the load at A required to maintain equilibrium of the beam is ?
    2. Relevant equations

    Principle of moments ? Sum of clockwise moments = sum of anti clockwise moments.

    3. The attempt at a solution

    Firstly, i decided to find the force due to the magnet.

    Taking moments about the midpoint,

    1kg x 10 x 0.5m = 0.5m x ( 0.6kg x 10 + force due to magnet )
    Which leads to the force being 4N.

    Subsequently, i went on to solve to question in moon.
    mass of load at A x 10/6 x 0.5m = 0.5m x ( 0.6kg x 10/6 + 4 )
    Which i got 3kg but the answer said that it was 1kg because gravity is not taken in account. ?!! Explain please thanks.
  2. jcsd
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