EK差=0.5*0.01*100=0.5J W=FS F=5NV均=s/t=12m/s V均=(V0+Vt)/2 Vt=22m/sEK差=0.5*75*(22-2)^2=15000 W=FS F=15000/60=250NF合=10N a=F/m=1m/s V=at=5m/s EK=0.5*10*5*5=125 Wf(阻力做功)=EK=125J fs=125 s=125/30=4.16米
