解：$(2)F_{浮}=G-F=2.5\ \text {N}- 1.5\ \text {N}=1\ \text {N}$
$(3)\frac {ρ}{ρ_水}=\frac {ρgV}{ρ_水gV}=\frac {G}{F_浮}=2.5 ，$得$ρ=2.5 ρ_水=2.5 ×10^{3}\ \text {kg/m}^3$
$(4)p=ρgh=2.5×10^{3}\ \text {kg/m}^3×10\ \text {N/kg}×2\ \text {m}=5×10^{4}\ \text {Pa}$
