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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

    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


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    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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