$解：(1)F=pS={ 5×10^5 }\ \text {Pa}×{ 120×10^{-4} }\ \text {m}^2={6000 }\ \text {N}$
$(2)W=Fs={ 6000 }\ \text{N}×{ 0.3 }\ \text{m}={ 1800 }\ \text{J}\\$
$(3)P=\frac {W_總}(cāng){t}=\frac {{ \frac {300}2×1800 }\ \text{J}}{{ 60 }\ \text{s}}={ 4500 }\ \text{W}$
