$ 解：(1)G_包=m_包g={ 8 }\ \text{kg}×10\ \text{N/kg}={ 80 }\ \text{N}\\$
$ W_包=G_包h={ 80 }\ \text {N}×{ 9 }\ \text {m}={ 720 }\ \text {J}$
$ (2)G_總=G+G_包=520\ \text {N}+80\ \text {N}=600\ \text {N}$
$ W=G_總h={ 600 }\ \text {N}×{ 9 }\ \text {m}={ 5400 }\ \text {J}$
$ P=\frac {W}{t}=\frac {{ 5400 }\ \text{J}}{{ 40×60 }\ \text{s}}={ 2.25 }\ \text{W}$
