1,(1)W总=FS=1000*2*2=4000J(2)W有=W总*η=4000*0.9=3600J(3)f=W有/S物=3600/2=1800J2,(1)P总=W总/t=2.5/5=0.5W(2)W总=F*2S物P总t=F*2S物2.5=F*2*0.5F=2.5N(3)η=f/nF=0.3*16/2*2.5=96%