解：?$(2)F_{壓}=G=(m_1+m_2)g=(60\ \mathrm {kg}+40\ \mathrm {kg})×10\ \mathrm {N/kg}=1000\ \mathrm {N}$?
?$p=\frac {F_{壓}}{S}=\frac {1000\ \mathrm {N}}{50×10^{-4}\ \mathrm {m^2}}=2×10^5\ \mathrm {Pa}$?
?$(3)F=f=0.08G=80\ \text {N}$?
?$W=fs={ 80 }\ \text{N}×{ 10×10^3 }\ \text{m}={ 8×10^5 }\ \text{J}$?
?$(4)v=\frac PF=\frac {400\ \text {W}}{80\ \text {N}}=5\ \text {m/s}$?
