NEET Sample Paper NEET Sample Test Paper-14

  • question_answer A ball is projected with a velocity of \[10\sqrt{2}\,m/s\]at angle of \[45{}^\circ \] with the horizontal from the top of a cliff 20 m high, with what velocity does the ball hit the ground?

    A) \[5\sqrt{3}\,m/s\]                    

    B) \[10\sqrt{3}\,m/s\]

    C) \[10\sqrt{6}\,m/s\]                  

    D)  \[10\sqrt{2}\,m/s\]

    Correct Answer: C

    Solution :

    Let the speed of projection be \[u=10\sqrt{2}\,m/s\]and the speed of the ball just before hitting the ground be v. Applying law of conservation of mechanical energy, we get: \[\frac{1}{2}m{{u}^{2}}+mgh=\frac{1}{2}m{{v}^{2}}\] \[\therefore \]    \[v=\sqrt{{{u}^{2}}+2gh}\] \[=\sqrt{200+2\times 10\times 20}\] \[=\sqrt{600}=10\sqrt{6}\,m/s\] Hence, the correction option is [c].


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