Question

一小石块从塔顶由静止开始下落,在到达地面的前的最后一秒内通过的位移是55米,不计空气阻力

Answer 1

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