CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2003

  • question_answer
    For a given velocity, a projectile has the same range R for two angles of projection if \[{{t}_{1}}\] and \[{{t}_{2}}\] are the time of flight in the two cases, then:

    A)  \[{{t}_{1}}{{t}_{2}}\propto R\]                  

    B)  \[{{t}_{1}}{{t}_{2}}\propto {{R}^{2}}\]

    C)  \[{{t}_{1}}{{t}_{2}}\propto \frac{1}{{{R}^{2}}}\]                

    D)  \[{{t}_{1}}{{t}_{2}}\propto \frac{1}{R}\]

    Correct Answer: A

    Solution :

    \[{{t}_{1}}=\frac{2u\,\sin \alpha }{g}\] \[{{t}_{2}}=\frac{2u\,\sin \,(90-\alpha )}{g}\] So, \[{{t}_{1}}\times {{t}_{2}}=2\frac{{{u}^{2}}}{{{g}^{2}}}\sin 2\alpha \]? or            \[{{t}_{1}}\times {{t}_{2}}=\frac{2R}{g}\]               \[\left( \because \,\,R=\frac{{{u}^{2}}\sin \,2\alpha }{g} \right)\]                 \[{{t}_{1}}\times {{t}_{2}}\propto R\]


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