An aeroplane flying at a constant speed, parallel to the horizontal ground, [ 3 ] kmabove …

Question

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 $$\Delta $$OA, A, OA1 = $${{\sqrt 3 } \over {\tan {{60}^o}}}$$ = 1 km

For $$\Delta $$OB1, B, OB1 = $${{\sqrt 3 } \over {\tan {{30}^o}}}$$ = 3km

As, a distance of 3 - 1 = 2 km is convered in 5 seconds.

Therefore the speed of the plane is

$${{2 \times 3600} \over 5}$$ = 1440 km/hr

Solutions · 1