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Motion In A Plane

Question
CBSEENPH11019966

(b) Shows that the projection angle θ0 for a projectile launched from the origin is given by,

straight theta subscript straight o space equals space tan to the power of negative 1 end exponent open parentheses space fraction numerator 4 straight h subscript straight m over denominator straight R end fraction close parentheses

where the symbols have their usual meaning.

Solution
Maximum space vertical space height. space straight h subscript straight m space equals fraction numerator space straight u subscript 0 squared space Sin squared straight theta space over denominator space 2 straight g end fraction space space space space space space space... space left parenthesis straight i right parenthesis

Horizontal space Range comma space straight R space equals space fraction numerator straight u subscript 0 to the power of 2 space end exponent Sin squared 2 straight theta space over denominator space straight g end fraction space space space space space space space space space space space space space... space left parenthesis ii right parenthesis

fraction numerator straight h subscript straight m space over denominator straight R end fraction equals space fraction numerator Sin squared straight theta space over denominator 2 Sin squared 2 straight theta end fraction space

space space space space space space space space equals space fraction numerator Sin space straight theta space cross times space Sin space straight theta space over denominator 2 space cross times 2 SinθCosθ end fraction

space space space space space space space space equals space fraction numerator sin space straight theta over denominator 4 space Cosθ end fraction space equals space tan space straight theta over 4

rightwards double arrow space tan space straight theta space equals space left parenthesis fraction numerator 4 hm over denominator straight R end fraction right parenthesis

rightwards double arrow space space straight theta space equals space tan to the power of negative 1 end exponent space open parentheses fraction numerator 4 hm over denominator straight R end fraction close parentheses