Go To Your Study Dashboard

Get Answers to all your Questions

header-bg

A bird is sitting on the top of a vertical pole 20 m high and its elevation from a point O on the ground is 45⁰. It flies off horizontally straight away from the point O.After one second, the elevation of the bird from O is reduced to 30⁰. Then the speed (in m/s) of the bird is :

Option 1)
$20\sqrt{2}$

Option 2)
$20\left ( \sqrt{3} -1\right )$

Option 3)
$40\left ( \sqrt{2} -1\right )$

Option 4)
$40\left ( \sqrt{3} -\sqrt{2}\right )$

Answers (1)

best_answer

As we learnt in

Height and Distances -

The height or length of an object or the distance between two distant objects can be determined with the help of trigonometric ratios.

-

$In \: \Delta PQQ \:, tan45^{\circ}=\frac{PQ}{OQ}$

$\Rightarrow OQ=20m$

$In \: \Delta {P}'{Q}'O, \: tan30^{\circ}=\frac{2O}{OQ'}\Rightarrow OQ'=20\sqrt{3}$

$Thus \: QQ'=20\sqrt{3}-20=20(\sqrt{3}-1)$

$Thus \: speed=20\left ( \sqrt{3}-1 \right ) \: \: =20\left ( \sqrt{3}-1 \right ) \: m/sec$

Option 1)

$20\sqrt{2}$

This option is incorrect

Option 2)

$20\left ( \sqrt{3} -1\right )$

This option is correct

Option 3)

$40\left ( \sqrt{2} -1\right )$

This option is incorrect

Option 4)

$40\left ( \sqrt{3} -\sqrt{2}\right )$

This option is incorrect

Posted by

Aadil

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE

Similar Questions

Trending Articles/News

anam-khan

How to crack JEE Mains 2025 in 1 month? Follow study plan, revise high-score topics, experts advice

anam-khan

IIT JEE aspirant from Bihar found hanging in Kota hostel; 17th suicide this year

anam-khan

JEE Main 2025 just a month away; section-wise preparation tips, important topics, strategies

Latest Question