JEE Main & Advanced
Mathematics
Trigonometric Equations
Question Bank
Height and Distance
question_answer
An aeroplane flying horizontally 1 km above the ground is observed at an elevation of 60o and after 10 seconds the elevation is observed to be\[{{30}^{o}}\]. The uniform speed of the aeroplane in \[km/h\] is [IIT 1965]
A)240
B)\[240\sqrt{3}\]
C)\[60\sqrt{3}\]
D)None of these
Correct Answer:
B
Solution :
\[d=H\cot {{30}^{o}}-H\cot {{60}^{o}};\] Time taken = 10 second Speed =\[\frac{\cot {{30}^{o}}-\cot {{60}^{o}}}{10}\times 60\times 60=240\sqrt{3}\].