第21页 - 伴你学八年级物理苏科版

物体E

36

$ 解：V=\frac {m_水}{ρ_水}=\frac { (140-40) g}{1\ \text {g/cm}^3}=100\ \text {cm}^3$

$ ρ=\frac {m_油 }{V}=\frac { (120-40) g}{100\ \text {cm}^3}=0.8\ \text {g/cm}^3$

$ 解：V_铁=\frac {m_铁}{ρ_铁}=\frac { 79\ \text {g}}{7.9\ \text {g/cm}^3}=10\ \text {cm}^3$

$ 是空心的，V_空=V-V_铁=12\ \text {cm}^3-10\ \text {cm}^3=2\ \text {cm}^3$

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

$ m_总=m_铁+m_水=79\ \text {g}+2\ \text {g}=81\ \text {g}$