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Motion In A Plane

Question
CBSEENPH11018530

The horizontal range of projectile is 4 times the maximum height attained by the projectile. What is the angle of projection?

Solution
Given, 
Horizontal range is equal to 4 times the maximum height attained by the projectile. 
Therefore, 
space space space space space space fraction numerator straight u squared over denominator 2 straight g end fraction sin 2 theta space equals 4 space fraction numerator u squared sin squared theta over denominator 2 g end fraction

i. e. comma space space space space sin space 2 theta space equals space 4 sin squared theta space space left square bracket because space sin space 2 theta space equals space 2 space sin theta space cos theta right square bracket

rightwards double arrow space space space space space space space space space fraction numerator sin space theta over denominator cos space theta end fraction space equals space 1

rightwards double arrow space space space space space space space space space space space tan space theta space equals space 1

rightwards double arrow space space space space space space space space space space space space theta space equals space 45 to the power of o
So, angle of projection is 45°.