The angle of elevation of an aeroplane from a point on the ground is 60°. After 15 seconds flight, the elevation changes to 30°. If the aeroplane is flying at a height of 1500√3 m, find the speed of the plane. A. 300 m/sec B. 200 m/sec C. 100 m/sec D. 150 m/sec Answer Workspace Report Discuss Answer with explanation Answer: Option B Explanation Given, the height of the aeroplane, BC = 1500 √3 meter Let, an aeroplane travelled distance BD = x metre in 15 seconds. And, AC = y metre ∴ AE = CE + AC = (x + y) m In ΔABC, tan 60° = BC AC 3 = 1500 3 y y = 1500 m Now, in ΔADE, tan 30° = DE AE 1 = 1500 3 3 x + y x + y = 4500 x + 1500 = 4500 x = 3000 m ∴ The aeroplane travelled 3000 m distance in 15 seconds. ∴ Speed = 3000 = 200 m/sec 15 Workspace
Discuss about the question