JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2007

  • question_answer
        A projectile can have the same range R for two angles of projection. If\[{{T}_{1}}\]and\[{{T}_{2}}\]be the times of flights in the two cases, then the product of the two times of flights is directly proportional to

    A)  \[\frac{1}{{{R}_{2}}}\]                                  

    B)  \[\frac{1}{R}\]

    C)  \[R\]                                    

    D)  \[{{R}^{2}}\]

    Correct Answer: C

    Solution :

                    We know that range of projectile is same for complementary angles i. e., for\[\theta \]and\[(90{}^\circ -\theta )\] \[\therefore \]  \[{{T}_{1}}=\frac{2u\sin \theta }{g}\]                 \[{{T}_{2}}=\frac{2u\sin (90{}^\circ -\theta )}{g}=\frac{2u\cos \theta }{g}\] and        \[R=\frac{{{u}^{2}}\sin 2\theta }{g}\] Therefore, \[{{T}_{1}}{{T}_{2}}=\frac{2u\sin \theta }{g}\times \frac{2u\cos \theta }{g}\]                 \[=\frac{2{{u}^{2}}(2\sin \theta \cos \theta )}{{{g}^{2}}}\]                 \[=\frac{2{{u}^{2}}(\sin 2\theta )}{{{g}^{2}}}=\frac{2R}{g}\] \[\therefore \]  \[{{T}_{1}}{{T}_{2}}\propto R\] 


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