Question

While landing at an airport, a pilot made an angle of depression of 20°. Average speed of the plane was 200 km/hr. The plane reached the ground after 54 seconds. Find the height at which the plane was when it started landing, (sin 20° = 0.342)

Answer 1

Let AC represent the initial height and point A represent the initial position of the plane.

Let point B represent the position where plane lands. Angle of depression = ∠EAB = 20°

Now, seg AE || seg BC 

∴ ∠ABC = ∠EAB … [Alternate angles] 

∴ ∠ABC = 20° 

Speed of the plane = 200 km/hr

∴ Distance travelled in 54 sec = speed × time

In right angled ∆ABC,

∴ The plane was at a height of 1026 m when it started landing.