AMU Medical AMU Solved Paper-2009

  • question_answer
    A ball is projected vertically upwards with a certain initial speed. Another ball of the same mass is projected at an angle of \[0{}^\circ \] with the vertical with the same initial speed. At highest points of their journey, the ratio of their potential energies will be

    A)  1 : 1                                      

    B)  2 : 1 

    C)   3 : 2                                     

    D)  4 : 1

    Correct Answer: D

    Solution :

                     For first ball At highest point, the kinetic energy is completely converted into its potential energy \[\therefore \]  \[mg{{h}_{1}}=\frac{1}{2}m{{u}^{2}}\] or            \[{{h}_{1}}=\frac{{{u}^{2}}}{2g}\] For second ball                 \[mg{{h}_{2}}=\frac{mg{{u}^{2}}{{\sin }^{2}}\theta }{2g}\]                                 \[=\frac{1}{2}m{{u}^{2}}{{\sin }^{2}}{{30}^{o}}\]                                 \[=\frac{1}{2}m{{u}^{2}}{{\left( \frac{1}{2} \right)}^{2}}\] or            \[{{h}_{2}}=\frac{{{u}^{2}}}{8g}\] \[\therefore \]  \[\frac{{{h}_{1}}}{{{h}_{2}}}=\frac{{{u}^{2}}}{2g}\times \frac{8g}{{{u}^{2}}}\] \[\Rightarrow \]               \[\frac{{{h}_{1}}}{{{h}_{2}}}=\frac{4}{1}\]


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