Water drops fall from a tap on the floor, 5 m below, at regular intervals of time, the first drop strikes the floor when the sixth drop begins to fall. The height at which the fourth drop will be from ground, at the instant when the first drop strikes the ground is _ _ _ _ m. ( g =10 ~m / s ² )

Step-by-step solution

Time for first drop to fall 5 m: 5 = 1 2 10 t^2 gives t = 1 s. Since the first drop strikes when the sixth begins, there are 5 intervals: each interval T = 1 5 = 0.2 s. When drop 1 hits the ground (at t = 1 s), drop 4 has been falling for t₄ = 1 - 3 0.2 = 0.4 s. Distance fallen by drop 4: s₄ = 1 2 10 (0.4)^2 = 0.8 m. Height of drop 4 above ground: 5 - 0.8 = 4.2 m.