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Density ρ question.

  1. Dec 9, 2009 #1
    1. The problem statement, all variables and given/known data
    Show that the change in the density ρ of a substance, when the temperature changes by ΔT,
    is given by Δρ = −βρ ΔT. (b) What is the fractional change in density of a lead sphere whose
    temperature decreases from 25°C to −40º C?


    2. Relevant equations
    βLead= 87x10-6

    3. The attempt at a solution
    ok i already go the first part, but i dont think im doing b right.

    im just plugging in (-40-25) for temperature, and the β of lead.
    so Δρ = −87x10-6ρ
    ρ=176.8Δρ

    i doubt thats the answer. am i misunderstanding the question here? or am i just doing something completely wrong?
     
  2. jcsd
  3. Dec 9, 2009 #2

    ideasrule

    User Avatar
    Homework Helper

    This is right, but the question asks for fractional change in density. That means the change in density divided by the density itself.
     
  4. Dec 9, 2009 #3
    oh... ok
    thank you :)
     
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