JEE Main & Advanced Physics Two Dimensional Motion Question Bank Self Evaluation Test - Motion in a Plane

  • question_answer
    A bullet is fired with a speed of \[1500\text{ }m\text{/}s\] in order to hit a target 100 m away. If \[g=10\text{ }m\text{/}{{s}^{2}}.\]The gun should be aimed

    A) 15 cm above the target

    B) 10 cm above the target

    C) 2.2 cm above the target

    D) directly towards the target

    Correct Answer: C

    Solution :

    [c] The bullet performs a horizontal journey of 100 cm with constant velocity of 1500 m/s. The bullet also performs a vertical journey of h with zero initial velocity and downward acceleration g.
    \[\therefore \] For horizontal journey, \[\text{time }\left( \text{t} \right)=\frac{\text{Distance}}{\text{Velocity}}\]
    \[\therefore \,\,\,t=\frac{100}{1500}=\frac{1}{15}\text{sec         }...\text{(1)}\]
    The bullet performs vertical journey for this time.
    For vertical journey, \[\text{h}\,\text{=}\,\text{ut+}\frac{\text{1}}{\text{2}}\text{g}{{\text{t}}^{\text{2}}}\]
    \[\text{h=0+}\frac{1}{2}\times 10\times {{\left( \frac{1}{15} \right)}^{2}}\]
    \[\text{or, h=}\frac{20}{9}\text{ cm = 2}\text{.2cm}\]


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