Question

有甲乙两条铁轨平行,甲轨上一列车正以a1=1m/s2的加速度出站,正前方1000m处的乙轨上有一列以40m/s的速度匀减

Answer 1

(1)

1000m = a1t^2/2 + v2t + a2t^2/2 = t^2/2 + 40t - t^2/2 = 40t

t = 1000/40 = 25s

25s后两车前端相遇

(2)

此时v1 = 25m/s v2 = 40 - 25 = 15m/s

200m = v1t + a1^2/2 + v2t + a2^2/2 = 25t + t^2/2 + 15t - t^2/2

= 40t

t = 200/40 = 5s

5s后两车开始互相离开