Dear1.54km/h=54000m/3600s=15m/s20m/s=(20km/1000) / (1h/3600)=72km/h 2.已知t=8min20s=500s v=3.0 X 10五次方m/s=300000m/s求:太阳和地球之间的距离s解:s=vtv=300000m/st=500ss=300000m/s x 500s =1.5 x 10的8次方(m)答:太阳和地球之间的距离为1.5 x 10的8次方米。 3.(1)s=vts=0.9km=900mt=5min=300s 得v=s/t=900m/300s=3m/s(2)3m/s=(3km/1000)/(...