The angle of elevation of an aircraft from a point A on the ground is 60° . After a flight of 30 seconds, the angle of…

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Let P and Q be the positions of aircraft at two different times.
$\tan 60^\circ = \sqrt{3} = \frac{3500\sqrt{3}}{x}$ (1)
$\Rightarrow x = 3500$ m ... (i) ($\frac{1}{2}$)
$\tan 30^\circ = \frac{1}{\sqrt{3}} = \frac{3500\sqrt{3}}{x+y} \Rightarrow x+y = 10500$ (1)
Using (i), we get $y = 7000$ ($\frac{1}{2}$)
$\therefore$ Speed of aircraft $= \frac{7000}{30}$ or $233. 3$ m/s approx. (1)