A paratrooper jumps from an aeroplane and opens a parachute after 2 s of free fall and starts deaccelerating with 3 m/s². At 10 m height from ground, while descending with the help of parachute, the speed of paratrooper is 5 m/s. The initial height of the airplane is m. (g = 10 m/s²)

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(1) 92.5. Free fall for 2 s: v = 10×2 = 20 m/s, distance = 1/2×10×4 = 20 m. Under the parachute the speed drops from 20 m/s to 5 m/s at 3 m/s²: v² = u² - 2as ⇒ 25 = 400 - 6s ⇒ s = 62.5 m. That leaves 10 m still to go. Initial height = 20 + 62.5 + 10 = 92.5 m.

A paratrooper jumps from an aeroplane and opens a parachute after 2 s of free fall and starts deaccelerating with 3 m/s². At 10 m height from ground, while descending with the help of parachute, the speed of paratrooper is 5 m/s. The initial height of the airplane is ______ m. (g = 10 m/s²)

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