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Energy (heat?)

  1. Dec 15, 2006 #1
    1. The problem statement, all variables and given/known data

    Suppose a steel strut with cross-sectional area 7.00x10^-4 m2 and length 2.50 m is bolted between two rigid bulkheads in the engine room of a submarine.
    (a) Calculate the change in temperature of the strut if it absorbs an energy of 3.00x10^5 J. °C

    2. Relevant equations

    Q = mcDeltaT
    DeltaT = Q/mc

    3. The attempt at a solution

    I tried using the formula DeltaT = Q/mc

    Delta T = 3.00 x 10^5/ m(448 J/kg *C)

    the problem im having is how do i find the mass?
  2. jcsd
  3. Dec 15, 2006 #2


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    Homework Helper

    Density of steel [tex]\rho _{steel} = 7.8 \times 10^3\ kg/m^3[/tex]
  4. Dec 15, 2006 #3
    I still dont understand how to solve this problem knowing the density of steel.
  5. Dec 15, 2006 #4

    Doc Al

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    Staff: Mentor

    Use it to find the mass of the steel.
  6. Dec 15, 2006 #5
    m = psteelV

    how do i find v?
    Last edited: Dec 15, 2006
  7. Dec 15, 2006 #6


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    Staff Emeritus
    Science Advisor

    No. You are given the cross sectional area and the length. Do you know how to calculate the volume from this information?
  8. Dec 15, 2006 #7
    okay i figure out how to solve this.

    it was P_steel x cross sec. area / length = m
  9. Dec 15, 2006 #8


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    Staff Emeritus
    Science Advisor

    Not quite: V=A*l (where A is the cross sec. area, l is the length). Above you had the correct forumla: m= ρ*V and so m= ρ*A*l
  10. Dec 15, 2006 #9
    oops, my mistake. yes i did mean m = p x A x l that was how i got the correct answer.

    Thanks for the correction and help.
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