A block of Iron

When a block of iron floats in mercury at 0 degrees C, a fraction K1 of its volume is submerged while at the temperature of 60 degrees, a fraction K2 is seen to be submerged. If the coefficient of volume expansion of iron is ∂Fe and that of mercury is ∂Hg, then the ratio K1/K2 is?

I got one answer as K1/K2 = 1+60∂Fe/1+60∂Hg
There is one more answer given as K1/K2 = 1-60∂Hg/1-60∂Fe

How do we get that?

2 Answers

23
qwerty ·

Vimmersed ρHgg = Vtotal ρFe g

so Vimmersed Vtotal = ρFeρHg

now ρ = mV = mVo(1+γΔτ) = ρo(1+γΔτ)

i.e ρ= ρo(1+γΔτ) ≈ ρo (1 - γΔτ) [ by binomail approximation

now the 2nd answer is given by directly using the equation for density as a function of T USING binomial approximation , while the first ans is exact . but therez not much difference

1
swordfish ·

Thanks qwerty

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