JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2005

  • question_answer
        A ball whose kinetic energy is E, is projected at an angle of\[45{}^\circ \]to the horizontal. The kinetic energy of the ball at the highest point of its flight will be:

    A)  E                                            

    B)  \[E/\sqrt{2}\]

    C)  E/2                                       

    D)  zero

    Correct Answer: C

    Solution :

                    At the highest point of its flight, vertical component of velocity is zero and only horizontal component is left which is \[{{u}_{x}}=u\cos \theta \] Given:      \[\theta =45{}^\circ \] \[\therefore \]  \[{{u}_{x}}=u\cos 45{}^\circ =\frac{u}{\sqrt{2}}\] Hence, at the highest point kinetic energy                 \[E=\frac{1}{2}mu_{x}^{2}\]                 \[=\frac{1}{2}m{{\left( \frac{u}{\sqrt{2}} \right)}^{2}}=\frac{1}{2}m\left( \frac{{{u}^{2}}}{2} \right)\]                 \[=\frac{E}{2}\]                 \[\left( \because \frac{1}{2}m{{u}^{2}}=E \right)\]


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