两半功是一样的设为W,
做前一半功用时:t1=W/P1=W/600.
做后一半功用时:t2=W/P2=W/300.
所以t1:t2=1:2,2t1=t2.
总共做功:2W.
全部平均功率:2W/(t1+t2)=2W/(3t1)=600*(2/3)=400w
两半功是一样的设为W,
做前一半功用时:t1=W/P1=W/600.
做后一半功用时:t2=W/P2=W/300.
所以t1:t2=1:2,2t1=t2.
总共做功:2W.
全部平均功率:2W/(t1+t2)=2W/(3t1)=600*(2/3)=400w