$ 解：(1)ρ=\frac {m }{V}=\frac {1.335\ \text {kg}}{ 1.5×10^{-4}\ \text {m}^3}=8.9×10^{3}\ \text {kg/m}^3 $
$ 是銅制成的$
$ (2)m_金=ρ_金V=19.3×10^{3}\ \text {kg/m}^3×1.5×10^{-4}\ \text {m}^3=2.895\ \text {kg}\\$
$ (3)V_B=\frac {m_B}{ρ}=\frac {1.78\ \text {kg}}{8.9×10^{3}\ \text {kg/m}^3}=2×10^{-4}\ \text {m}^3$
