JEE Mains · Physics · STD 11 - 3.2 motion in plane

એક પ્રક્ષિપ્ત કરેલો પદાર્થ \( y = 2x -9x^2\) મુજબ ગતિ કરે છે. જો તેને \(\theta_0\) ના ખૂણે \(v_0\) વેગથી પ્રક્ષિપ્ત કરવામાં આવેલ હોય તો .... \((g = 10\,ms^{-2}\))

A \({\theta _0} = {\cos ^{ - 1}}\,\left( {\frac{1}{{\sqrt 5 }}} \right)\) અને \({v_0} = \frac{5}{3}\,m{s^{ - 1}}\)
B \({\theta _0} = {\cos ^{ - 1}}\,\left( {\frac{2}{{\sqrt 5 }}} \right)\) અને \({v_0} = \frac{3}{5}\,m{s^{ - 1}}\)
C \({\theta _0} = {\sin ^{ - 1}}\,\left( {\frac{2}{{\sqrt 5 }}} \right)\) અને \({v_0} = \frac{3}{5}\,m{s^{ - 1}}\)
D \({\theta _0} = {\sin ^{ - 1}}\,\left( {\frac{1}{{\sqrt 5 }}} \right)\) અને \({v_0} = \frac{5}{3}\,m{s^{ - 1}}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \({\theta _0} = {\cos ^{ - 1}}\,\left( {\frac{1}{{\sqrt 5 }}} \right)\) અને \({v_0} = \frac{5}{3}\,m{s^{ - 1}}\)

Step-by-step Solution

Detailed explanation

\begin{array}{l} Equation\,of\,trajectory\,is\,given\,as\\ \,\,\,\,\,\,\,\,\,\,y = 2x - 9{x^2}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...\left( A \right)\\ \,\,\,Comparing\,with\,equation\,\,\,\,\,\,\,\,\,\,\,\,\\ \,\,\,\,\,\,\,\,\,y = \,X\,\tan \,\theta -…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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