h=1/2gt^2
h'=1/2g(t-1)^2
h-h'
=1/2g[t^2-(t-1)^2]
=5(t^2-t^2+2t-1)
=10t-5=55
10t=60
t=6s为什么等于55题不是告诉你了吗？最后一秒内通过的位移是55米