How long does a stone fall if in the last 2 seconds it has flown 60 m?

Task data: t1 (time before the stone falls) = 2 s; S (the path of the stone for the time t1) = 60 m; we consider the fall free.

Reference values: g (acceleration due to gravity) ≈ 10 m / s2.

1) The speed of the stone until the last two seconds of the fall: S = V * t1 + g * t1 ^ 2/2; V0 = (S – g * t1 ^ 2/2) / t1 = (60 – 10 * 2 ^ 2/2) / 2 = 20 m / s.

2) The time of the stone falling to the last 2 s: V = g * t2; t2 = V / g = 20/10 = 2 s.

3) The total duration of the fall: t = t1 + t2 = 2 + 2 = 4 s.

Answer: The stone fell in 4 seconds.