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Homework Help: Mechanical properties of matter problem,

  1. Feb 22, 2010 #1
    Mechanical properties of matter problem, urgent!!!

    1. The problem statement, all variables and given/known data
    When a beaker partially filled with water is placed on an accurate scale, the scale reads 22g . If a piece of metal with density 3800 kg/m^3 and volume 2,4 cm^3 is suspended by a thin string so that the metal is submerged in the water but does not rest at the bottom of the beaker, what does the scale read?

    2. Relevant equations

    Fb= mg-Fs
    N(y) + Fs(Y)+mg(-y)+(22*g)(-y)=0

    3. The attempt at a solution
    V=2,4cm^3=2.4*10^-6 m^3 density= 3800 kg/m^3
    mass metal= 0,00912 [kg]
    System Metall: Fs+ Fb+ mg= 0
    Fb= mg-Fs
    System: Beaker + Metall+ H20
    System : Beaker + metall + h20
    N(y) + Fs(Y)+mg(-y)+(22*g)(-y)=0
    N= 22*g+ Fb
    solving for N= 9.8 / 24.4*10^-3)

    Is this the right way of solving the problem? Are there other methods-easier? In that case please let me know, asap i have a crucial-grade determining -test in 2 days!!!

    Btw , another question, how come in the equation for the Bigger system , one disregards the buoyancy force but then is allowed to plug it in ?
    Thanks in advance
  2. jcsd
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