JEE Main & Advanced Physics Two Dimensional Motion JEE PYQ - Two Dimensional Relative Motion

  • question_answer
    A ball whose kinetic energy is E, is projected at an angle of \[{{45}^{o}}\] to the horizontal. The kinetic energy of the ball at the highest point of its flight will be                                               [AIEEE 2002]

    A) E

    B) \[E/\sqrt{2}\]

    C) \[E/2\]

    D) zero

    Correct Answer: C

    Solution :

    [c] At the highest point of its flight, vertical component of velocity is zero and only horizontal component is left. Which is as, there is no acceleration of particle in horizontal component A velocity remains constant
    \[{{u}_{x}}=u\cos \theta \]
    Given      \[\theta ={{45}^{o}}\]
    \[\therefore \]      \[{{u}_{x}}=u\cos {{45}^{o}}=\frac{u}{\sqrt{2}}\]
                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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