JEE Main & Advanced Physics Motion in a Straight Line / सरल रेखा में गति Question Bank Motion Under Gravity

  • question_answer
    A body is released from the top of a tower of height \[h\]. It takes \[v=\frac{1}{2}b{{t}^{2}}+{{v}_{0}}\] sec to reach the ground. Where will be the ball after time \[t/2\] sec           [NCERT 1981; MP PMT 2004]

    A)             At \[h/2\]from the ground

    B)             At \[h/4\] from the ground

    C)             Depends upon mass and volume of the body

    D)             At \[3h/4\]  from the ground

    Correct Answer: D

    Solution :

                    Let the body after time \[t/2\]be at x from the top, then                        \[x=\frac{1}{2}g\frac{{{t}^{2}}}{4}=\frac{g{{t}^{2}}}{8}\]                         ?(i)             \[h=\frac{1}{2}g{{t}^{2}}\]                                   ?(ii)             Eliminate t from (i) and (ii), we get \[x=\frac{h}{4}\]             \[\therefore \] Height of the body from the ground \[=h-\frac{h}{4}=\frac{3h}{4}\]


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