QJEEM18Ma2706: JEE Main 2018 Mathematics - Class 12 JEEM18Ma2706 Solution: An aeroplane flying at a constant speed, parallel to the…

Question

Verified Solution • 2025–26 Session moderate

An aeroplane flying at a constant speed, parallel to the horizontal ground,

\sqrt{3}

kmabove it, is obsered at an elevation of

60^{o}

from a point on the ground. If, after five seconds, its elevation from the same point, is

30^{o}

, then the speed (in km / hr) of the aeroplane, is :

Accepted Answer

For

Δ

OA, A, OA₁ =

\frac{\sqrt{3}}{\tan 60^{o}}

= 1 km

For

Δ

OB₁, B, OB₁ =

\frac{\sqrt{3}}{\tan 30^{o}}

= 3km

As, a distance of 3

-

1 = 2 km is convered in 5 seconds.

Therefore the speed of the plane is

\frac{2 \times 3600}{5}

= 1440 km/hr

Step-by-Step Verified Solution