设井深H
石头行程时间+声音行程时间= t
√(2H/g) + H/v = t
√(2H/g) = t - H/v
2H/g = t^2-2tH/v + H^2/v^2
gH^2-2v(v+gt)H+gv^2t^2 = 0
H = 2v { v+gt+√(v^2+2vgt) } / (2g)
设井深H
石头行程时间+声音行程时间= t
√(2H/g) + H/v = t
√(2H/g) = t - H/v
2H/g = t^2-2tH/v + H^2/v^2
gH^2-2v(v+gt)H+gv^2t^2 = 0
H = 2v { v+gt+√(v^2+2vgt) } / (2g)