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Express the density of a solid substance varying with temperature

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Feb23-06, 11:19 PM
P: 176
I need to show that the density of a solid substance varies with temperature as d = d0(1 - 3aT), where a is the thermal coefficient and T is the change in temperature.

I know V = V0 (1 + 3aT) and V = m/d. Since m is constant,

d0 = d(1 + 3aT)
d0 - d03aT = d + d3aT - d03aT
d0(1 - 3aT) = d +3aT(d - d0)

Am I now supposed to assume that the d only changes a little compared to d0, so that (d - d0) = 0?
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Feb24-06, 07:21 AM
HW Helper
P: 507
do = d(1 + 3aT)
d = do/(1+3aT) = do(1+3aT)^-1

now expanding using binomial theorem and as a is very small the higher terms can be neglected, gives

d = do(1- 3aT + ....)


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