以乙为参考系,则甲的初始相对速度为-5m/s,相对加速度为0.5m/s^2,s=v0t+0.5at^2,即75=-5t+0.25t^2,解得t=30s,即30s追上乙.甲离出发点:0.5at^2=0.25*900=225m
2、以甲的出发点为坐标原点,甲的坐标是0.5at^2=0.25t^2,乙的坐标是75+5t,相距:75+5t-0.25t^2,当t=-b/2a=10s时距离最大,为:75+50-25=100m
以乙为参考系,则甲的初始相对速度为-5m/s,相对加速度为0.5m/s^2,s=v0t+0.5at^2,即75=-5t+0.25t^2,解得t=30s,即30s追上乙.甲离出发点:0.5at^2=0.25*900=225m
2、以甲的出发点为坐标原点,甲的坐标是0.5at^2=0.25t^2,乙的坐标是75+5t,相距:75+5t-0.25t^2,当t=-b/2a=10s时距离最大,为:75+50-25=100m