最后1s内位移h=(1/2)gt^2-(1/2)g(t-1)^2=0.5*10[t^2-(t-1)^2]=5*(2t-1)
45=5(2t-1)
落地所需时间t=5s
下落高度H=(1/2)gt^2=0.5*10*(5*5)=125m
落地时的速度V=gt=10*5=50m/s