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第82页

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$ 解：V_铝=\frac {m_铝}{ρ_铝}=\frac {27\ \text {g}}{2.7\ \text {g/cm}^3}=10\ \text {cm}^3$

$m_液=m_总-m_铝=43\ \text {g}- 27\ \text {g}=16\ \text {g}$

$V_液=V_球-V_铝=30\ \text {cm}^3-10\ \text {cm}^3=20\ \text {cm}^3$

$ρ_液=\frac {m_液 }{V_液}=\frac {16\ \text {g}}{ 20\ \text {cm}^3}=0.8\ \text {g/cm}^3$

$ 解：(1)m_水=m_冰=ρ_冰V_冰=0.9\ \text {g/cm}^3×80\ \text {cm}^3=72\ \text {g}$

$V_水=\frac {m_水}{ρ_水}=\frac {72\ \text {g}}{1\ \text {g/cm}^3}=72\ \text {cm}^3$

$(2)m_水=ρ_水V_水=1\ \text {g/cm}^3×60\ \text {cm}^3=60\ \text {g}$

$ρ_{盐水}=\frac {m_{盐水} }{V_{盐水}}=\frac {(13.5+60) g}{70\ \text {cm}^3}=1.05\ \text {g/cm}^3=1.05×10^3 \mathrm{kg/m^3}$